eDtdaiigsttiiteoarnl PlTahent Review Taster issue 2023 Enjoy travelling to Beautiful plants and Science, news, opinion a world of gardens how to grow them and more in every issue

Editor’s welcome Welcome to this special edition of The Plant Review The Plant Review As you are reading this, I’m going to make a shrewd Editor: James Armitage guess that you are interested in plants. Great, isn’t it?! Contributing Editor: Mike Grant To have been bitten by the plant bug is a huge slice of Designer: Simon Garbutt luck. No other pastime offers such an infinite source of Art Editor: Mark Timothy fascination, beauty and enrichment for the soul. Colour Reproduction: However, I sometimes find it does present one problem. Anthony Masi With a hobby where there is so much to know and Production Manager: Diana Levy everything is of interest I can start to feel overwhelmed. Head of Editorial: Tom Howard What do I learn next? What am I missing out on? Advertising to: Louise Bowering, And that’s where The Plant Review is invaluable. Special Publications Manager, Four times a year, like your dream botanic garden RHS Media (address above) between two covers, it delivers a diverse medley of Tel: 01733 294679 some of the most wonderful plants the world has to Fax: 01733 341633 offer, bringing you content that you will find nowhere Email: [email protected] else, so that you can rest assured the best of life is not passing you by. Subscriptions, back issues and missed issue queries: This taster issue contains a selection of articles that The Plant Review, RHS Membership have appeared in The Plant Review over the last couple Subscriptions, PO Box 313, of years, written by authors who are a mixture of London SW1P 9YR, UK amateurs and professionals but who all share your love Tel: 020 3176 5820 of growing and studying plants. I hope from it you will Email: [email protected] discover some plants you didn’t know before and gain Online renewal: rhs.org.uk/ an idea of what The Plant Review has to offer. plantreview James Armitage, Editor Opinions expressed by authors and services offered by advertisers are not specifically endorsed by the editors or the Royal Horticultural Society © Royal Horticultural Society 2023 Registered Charity No. 222879 / SC038262 Published by: RHS Media, 3rd Floor, Stuart House, City Road, Peterborough PE1 1QF PlaThne t Review Subscribe today rhs.org.uk/theplantreview or tel: 020 3176 5810 2 The Plant Review

Moss roses Arising fewer than 300 years ago, as historic roses the Mosses are comparative youngbloods. However, the spicy aroma of their scent glands makes them the most evocative of flowers. ARTWORK: DEBORAH LAMBKIN

News Keeping in the know in the world of plants Succulent RHS1 RHS storms Chelsea The Chelsea Plant of the Year competition has been won by × Semponium ‘Destiny’, a dark-leaved x2xxxxx intergeneric hybrid between Sempervivum ‘Green Ice’ and Aeonium ‘Ice Warrior’, combining frost 1 × Semponium ‘Destiny’ 3 RHS resistance from the former with the dramatic is the Chelsea Plant of the FORREST & KIM STARR / WIKIMEDIA COMMONS foliage of the latter. It was raised by Daniel Michael of Surreal Succulents. Year 2022. Runners up were 2 Armeria Armeria ‘Dreamland’ and Salvia Pink Amistad ‘Dreamland’ and (‘Arggr17-011’) were runners up. ‘Dreamland’ was 3 Salvia ‘Pink Amistad’. developed in Australia from Armeria pseudarmeria and is used as a drought-tolerant border plant with perennial with deeply saturated pink flowers a long flowering season. Pink Amistad is a version raised by Gebr Rotteveel while Rhododendron of the old favourite ‘Amistad’, a hybrid between Starstyle Pink (‘Azaare01’) is a very compact Salvia guaranitica and Salvia gesneriiflora found in plant with a similar mutation to the old cultivar a garden near Buenos Aires in 2007 which has sold R. stenopetalum ‘Linearifolium’ bred by Hilde and over four million plants. Pink Amistad is a pink- Matthijs Barendse. flowered version found by Argentinian salvia breeder Rolando Uria. For those wishing to mix ornamental and nutritional value, broccoli ‘Purplelicious’, bred by Other entries were Forsythia × intermedia Rick Grazzini and Ard Ammerlaan, has attractive ‘Discovery’ with white-margined leaves, bred by Hillier Nurseries Ltd and Buddleja davidii Little Ruby (‘Botex 006’), a bright, dwarf buddleja bred for patio use. Geranium × cantabrigiense ‘Intense’ is a compact Araceae get racy for gnats True blue? Arisaema may have joined the list It has been reported in the journal of plants that offer a sexual lure New Phytologist that the blue fruits to pollinators. Species had been of Lantana × strigocamara (right) assumed to emit a mushroom have been shown to be due not to aroma to attract fungus gnats. pigmentation but to microscopic However, a paper in the journal structures in the skin which reflect Plants People Planet reveals almost wavelengths in such a way that they all dead gnats found in spathes of are seen as blue. This is fairly A. angustatum and A. peninsulae common in animals (peacocks’ tails are male suggesting plants might for example) but in plants is other- also mimic female gnat pheromone. wise known only in Viburnum tinus. doi.org/10.1002/ppp3.10261 doi:10.1111/nph.18262 4 The Plant Review

4RHS RHS 5 Volunteer RHS RHS RHS 6 for virtual dig Other noteworthy entries for Chelsea Plant of the Volunteers are invited to help with Year 2022 included: a new RHS venture called Digital 4 Forsythia × intermedia Dig, a new National Lottery ‘Discovery’, 5 Buddleja Heritage-funded project to uncover davidii Little Ruby Britain’s lost plant nurseries. (‘Botex 006’), 6 Geranium × cantabrigiense ‘Intense’, The RHS has a unique collection 7 Rhododendron Starstyle of about 28,000 nursery catalogues, Pink (‘Azaare01’), and dating to 1612, which has never 8 broccoli ‘Purpleicious’. been curated or seen by the public. This collection constitutes a 78 fascinating biological and social purple leaves that keep their colour even archive, tracking gardening after cooking. infrastructure over time. rhs.org.uk/shows-events/rhs-chelsea-flower-show/ news/2022/plant-of-the-year Volunteer transcribers will work remotely and flexibly to transcribe Snowdrops bag Brickell Award MARGARET MACLENNAN plant lists from 60 early nursery Plant Heritage has awarded the catalogues with a view to creating 2022 Brickell Award for excellence Galanthus ‘Mother Goose’ an open-access online research in cultivated plant conservation to resource. The catalogues represent Margaret and David MacLennan nurseries from the UK and Europe, for their Galanthus collection. including John Cree’s Hortus Addle- Located in Carlisle, Cumbria, and stonensis (1829) and Voorhelm & containing 2,000 taxa, each year Schneevoogt’s Catalogus of Dutch quantities of spare snowdrop bulbs flower-roots (1798). are donated from the collection to botanic gardens, RHS gardens and A further volunteering National Trust properties. opportunity is soon to be launched plantheritage.org.uk to help geotag the whole nursery catalogue that covers over 4,000 Digital taster edition individual nurseries. Recording latitude and longitude coordinates for each nursery will help create the first national map of the UK’s plant nurseries through time. Contact [email protected] Cambridge acclaim University of Cambridge Herbarium has been officially given Designated Status by the Arts Council England, recognizing the herbarium’s natural history collections as being of great historical and scientific importance for the country. Established in 1761, the herbarium holds an estimated 1.1 million plant specimens from all over the world, making it one of the largest collections of pressed and dried plant specimens in the UK. 5

Paeonia ‘GleamCAROLINE STONEROYAL BOTANIC GARDENS, KEW of Light’ was a worthy winner New waterlily of Plant is a world- Heritage’s beater Threatened Plant of the Year A huge Victoria lurking in the competition. herbarium at Royal Botanic Gardens, Kew, for 177 years has Peony wins Plant Heritage’s been named as a new species and threatened plant prize the largest waterlily in the world. Paeonia ‘Gleam of Light’ has been crowned the winner of Plant Long suspecting that there was Heritage’s Threatened Plant of the Year 2022 competition. A an undescribed third species of variegated Aeonium and a rose named after Sir Winston Churchill Victoria, Kew senior botanical were joint winners of the People’s Choice award. horticulturist Carlos Magdalena grew seeds accessioned from The perfumed, free-flowering perennial was first recorded in Bolivia. Resultant plants showed Kelways Nursery’s 1954 catalogue but hasn’t been commercially a different seed shape and prickle available for over five years. It was saved from extinction by Plant distribution from V. amazonica and Guardian, Roz Cooper. Roz has been able to provide plant material V. cruziana and, with leaves to more to Caroline Stone (see pp12–17), further helping to re-build numbers. than 3m across, represented the world’s largest waterlily species. Aeonium arboreum ‘Albovariegatum’ has rosettes that change Described in the journal Plant colour from creamy white to lime green, cream and pink variegation Systematics and Evolution as and forms part of Melanie Lewis’s Shropshire Collection of Aeonium. V. boliviana, in the wild the new species grows in the Llanos de Rosa ‘Sir Winston Churchill’, despite its association with such Moxos, Beni province, Bolivia, but a well-known figure, became lost from UK horticulture. As part of all three species are at the Princess a project to bring together all the plants named after Churchill in a of Wales Conservatory, Kew. National Plant Collection, John Moore eventually tracked it down doi.org/10.3389/fpls.2022.883151 in South Australia’s David Ruston Garden, where over 50,000 rose cultivars are grown. Bud material was sent back to the UK, where it was grafted and now forms part of a ‘living archive’ of Churchill- related plants at Churchill College, Cambridge, complementing the archive papers of Churchill also held on site. Its future is looking brighter, as plants have been shared with Cambridge Botanic Garden and Blenheim Palace. plantheritage.org.uk Catnip found repellent Life on the edge ANDREAS FLEISCHMANN Feline attraction to catnip, Nepeta The behaviour of the sundew flower cataria, is well known but it was fly, Toxomerus basalis, has been Sundew flower fly larva uncertain why cats also inflicted investigated in a paper in the Journal damage by licking and chewing the of Tropical Ecology. Females of this plants. Now a paper in iScience has species lay eggs on leaves of shown that damaged Nepeta tissue insectivorous Drosera species but shows increased emission of iridoids studiously avoid the traps. The that act as mosquito repellent. emerging larvae collide with the These are transferred to cats as they sticky hairs but a coating of slime roll ecstatically among the catnip, renders them impervious and may helping them stay arthropod free. also act as chemical camouflage. doi.org/10.1016/j.isci.2022.104455 doi.org/10.1017/S0266467422000128 6 The Plant Review

QING-GONG MAO News CHRISTIE’S IMAGES, THE LUCIAN FREUD ARCHIVE Big begonia boggles boffins A newly described species of Begonia has surprised scientists by going unnoticed, despite its huge size. Described by Chinese botanists in the journal PhytoKeys, Begonia giganticaulis is, at 4m, the tallest species of its genus recorded in the whole of Asia. It is currently known from at least two localities in the county of Mêdog in Tibet where it grows on slopes under forest along streams at elevations of 450–1,400m. However, populations are estimated to number only about 1,000 individuals in total. Begonia giganticaulis is perennial, evergreen and dioecious. ‘It is most similar to Begonia longifolia and Begonia acetosella,’ said Professor Daike Tian, a researcher with Shanghai Chenshan Botanical Garden, ‘But clearly differs from the former in being dioecious rather than monoecious, its longer inflorescence, and unique fruit shape. From the latter it differs in having six rather than four tepals and three- rather than four-loculed ovaries.’ It also grows up to twice as tall as either species. doi: 10.3897/phytokeys.187.75854 Hedge fund ‘Still Life With Zimmerlinde’ Freud on plants The Tree Council’s new Talk to This autumn, the Garden Museum the Hedge programme has been will present the first exhibition of awarded a £500,000 grant from Lucian Freud’s paintings of plants the £6 million Trees Call to Action and gardens. Freud was a prolific Fund. Talk to the Hedge starts in painter of plants and zimmerlinde, June this year and is intended to Sparmannia africana, grown in Vienna protect and promote the UK’s by his grandfather, Sigmund, was an hedgerows through a series of unofficial Freud family emblem. funded projects. More than 50% Lucian Freud: Plant Portraits runs of UK hedgerows have been lost from 14 October 2022–5 March 2023 since the Second World War. and coincides with the centenary of treecouncil.org.uk the artist’s birth (8 December 1922). Digital taster edition 7

The hardy boys Daniel Hinkley discusses 25 years of observing begonias in the wild and evaluating them for hardiness The size of Begonia aff. silletensis (above) in Arunachal Pradesh is clearly evident when stacked up against the author’s travelling companion, Leonard Foltz. The Five Fingers range of mountains in northern Vietnam is rich Begonia habitat (main picture). 8 The Plant Review

Hardy begonias Caption in here PHOTOGRAPHY BY DANIEL J HINKLEY UNLESS OTHERWISE STATED MUCH WATER HAS flowed under the please Ibus, bridge since 1753, when botanist volorumque ex es Charles Plumier honoured Michel Bégon, secae exerib usda a former governor of the French colony of Saint dolorum aut Dominque (now Haiti), with a genus name later estores accepted by Linnaeus. Since then, Begonia has sendistetum enjoyed its fair share of horticultural limelight, both in the frenzied sport of plant collecting and Digital taster edition among the general public. From bedding favourites Begonia Semperflorens Cultorum Group, through ornate selections of B. × tuberhybrida, to cosseted tropical species in conservatories, the genus is a match for the manias of orchids, ferns and tulips. With new taxa still being described, the genus Begonia is estimated to have just over 2,000 species, with the tropics of Central and South America and Africa holding the lion’s share. The temperate species, on which this article dwells, are found in considerable numbers throughout South East Asia. The thrill of the hunt Over the course of three decades, I have found immense satisfaction in looking at wild plants from areas that might correspond more or less to the minimum and maximum temperatures and winter rainfall patterns of the Pacific Northwest. (47.8°N, average minimum temperature 4°C, average yearly rainfall 73.5cm). The products of my endeavors have been grown in two gardens on the Kitsap Peninsula, approximately 24km west of Seattle across the Puget Sound: Heronswood Garden (USDA Zone 8) and Windcliff (Zone 8b). Though my interests run the gamut of herbaceous and woody plants, a perusal of the inventories of both gardens reveals a greater interest in some genera than others. Represented are respectable collections of Acer, Araliaceae, Disporum, Hydrangea, Illicium, Magnolia, Maianthemum, Paris and Polygonatum besides the subject at hand, Begonia. Unknown Begonia species (top) at Five Fingers in northern Vietnam. Begonia flaviflora DJHM 13027 (middle) from Myanmar has proved amenable to cultivation in a bright spot. Begonia baviensis (bottom) from Five Fingers and Phan Xi Păng, Vietnam, is a suitable subject for pot culture. 9

In 1995, duing my first trip to eastern Nepal The Plant Review with Bleddyn and Sue Wynn-Jones, our notes indicate that five Begonia collections were made, none of which are extant in our respective collections today. Other than Begonia grandis, I did not then consider the genus adaptable to the cool maritime summers and arctic winter outbreaks of the Pacific Northwest (PNW). Those seed collections made in Nepal that year, from lower elevations, did not establish, which only reinforced my opinion of their unreliability as long-term garden perennials. Branching out My conversion to full-throttle appreciation of the genus came in 1996 and 1998 during the first two of five trips to the slopes of Emei Shan in Sichuan, China. Common on the lower slopes were impressive colonies of Begonia pedatifida, while B. emeiensis, a distinctive species endemic to this mountain occurred at slightly higher elevations. They have proved to be bullet-proof, withstanding, without complaint or protection, fully 25 years of arctic assault. Begonia pedatifida DJHC 98473 produces, from slowly spreading rhizomes, mounds, to 0.3m, of deeply incised peltate foliage, 20 × 20cm, with reddish tints to the petioles and leaf veins. Monecious, pink to white flowers appear in late summer in the PNW on inflorescences rising just above the foliage. Subsequent trips to Emei Shan have revealed clones with solid burgundy as well as silvery white foliage. Begonia emeiensis DJHC 98479 produces a network of stout rhizomes from which solid green, distinctively coarse-textured foliage, 15 × 10cm, emerges in spring. Monecious pink flowers are produced under the foliage late in the season. Fairly large bulbils appear in late summer at the juncture of the leaf blade and petiole, providing an easy method of propagation. The substantial rhizome of this species will mold to vertical surfaces; this in combination with its hardiness makes it a good candidate for green walls. I did collect seed of Begonia limprichtii DJHC 98418 from the same mountain in 1998 and established but then lost resultant plants. Forming small clumps with relatively large leaves, it has a bluish green iridescence, made apparent only under the correct light conditions of deep shade, that is near mystical. In 1997, I collected bulbils of Begonia grandis HC 970628 near Kochi on the island of Honshu, Japan. As frosts had already occurred in early November that year, it was not until the following growing season the decidedly more ornamental features 10

BLEDDYN WYNN-JONES Hardy begonias The deeply cut foliage of Begonia pedatifida of this collection, over what was being cultivated (opposite, top), growing on Emei Shan. under this name at Heronswood, were noted. What we introduced as ‘Heron’s Pirouette’ possesses a Begonia pedatifida DJHC 98473 (opposite, significantly longer, pensile panicle of pink flowers middle) has appealing pink and white flowers. in August and September. The nuisance of its bulbils resowing in the garden is no less than other clones I Begonia emeiensis (opposite, bottom), have grown, though because of its ease of propagation growing on Emei Shan. it has become commonplace in the US nursery trade. Begonia grandis ‘Heron’s Pirouette’ (top) A return trip to north-eastern Nepal in 2002, has long panicles of pink flowers. again with the Wynn-Joneses, yielded an additional six collections, all noted as growing on a thin, Begonia HWJK 2424 (above) from Nepal mossy substrate adhering to rock surfaces. As a probably represents a new species. general rule, this habitat does not auger well for garden-worthiness, though an exception has been Digital taster edition HWJK 2424. Collected as Begonia annulata from along a steep descent to the Mewa Khola at 2,080m, it is now obvious this was an incorrect identification and that it probably represents a new species. Broad and deeply rugose leaves to 17.5 × 12.5cm are hand- somely banded in silver with some red staining. However, in the coolth of a PNW summer, the foliage does not emerge until mid-July. In early September, erect panicles to 20cm carry large pink to white, sharply serrate petals opening from red, densely-bristled buds. Adventures in Vietnam More than 16 trips to northern Vietnam since 1999 have made me keenly aware of the richness of its flora as well as its generally understudied nature. Collection notes indicate that 42 seed collections of Begonia have been made, with only a fraction becoming established in the garden. Those successfully established have been fully hardy in the PNW if mulched in autumn with dry wood shavings, though only a small proportion of the 60 or so species native to Vietnam have been trialed. Begonia baviensis is relatively common at mid- elevations on both the Five Fingers range as well as the more frequently trekked Phan Xi Păng. The strikingly red-bristled stems, leaves and flower buds make it worth growing, if only in a container. One of the hardiest caned species I have grown thus far is another collection from Five Fingers made in 2013. In cultivation Begonia aff. edulis DJHV 13055 produces 1.2m-long stems clad with broadly triangular, deeply cleft leaves with broad bands of pewter. The flowers are borne very late, comprised of short terminal panicles carrying small white flowers. This, too, is protected in late autumn before heavy frosts arrive and has proven hardy through all winters since 2014. At lower to mid elevations throughout the region is found the easily recognized Begonia sizemoreae, 11

with highly variably coloured or variegated Begonia sizemoreae DJHV leaves encrusted with bristles suggesting more a 13034 (top) is a collection marine invertebrate than a plant. Though this from Vietnam. remains part Begonia palmata DJHM of the collections in the woodland at Heronswood, 13008 (above and right) it frequently does not emerge until the beginning is from Myanmar. of September. My collection of this species, DJHV 13034, has produced a magnificent specimen at the 2,655m, no one could possibly miss the Gunnera- Amazon Spheres in downtown Seattle. sized plants of Begonia aff. silletensis DJHAP 18001 Meanderings in Myanmar growing in a moist, tropical forest environment. The In 2013, I ventured to northern Myanmar to take distinctively glossy leaves can reach around 75 × 75cm part in an eco-trekking enterprise, taking one of while at the base, in October, are found ping pong two open routes to the summit of Phangan Razi at ball-sized berries of mottled red on short pedicels 3,380m. The razorback ridge leading to the summit to 15cm. Rodent dung intermixed with partially was still pristine and untrodden with an astonishing eaten fruit suggest the means of dispersal. The array of woody and herbaceous plants, an overstory fruit follow large, 6–7cm, nodding and exceedingly of Abies delavayi and with bands of eastern hoolock fragrant flowers. Thus far, this has proven to be an gibbons serenading us at dusk and dawn. It was exceptionally adaptable container plant tolerating during these days upon the ridge, while afflicted well the consistent coolness of the PNW climate. with a subdermal infection of nematodes acquired from a leech bite, that we collected seed of Begonia At the top of the Mayodia Pass, Begonia ascendens palmata and B. flaviflora. is common, forming beefy clumps of rounded leaves to 12 × 12cm, each centrally blotched in The former, Begonia palmata DJHM 13008, whose seductive plum-coloured, silver-variegated foliage The Plant Review demanded attention, has produced from a single seed parent a wide array of phenotypes. Those fully unpigmented are nearly too robust in the garden, forming luscious mounds of deep green to 75 × 75cm, somewhat concealing striking pink flowers in late season. On the other end of the spectrum are seedlings nearly identical to the ravishingly pigmented plants we witnessed along the trail. Under cultivation, these are noticeably weaker and slightly less hardy. Pricking out small seedling will virtually guarantee clones of differing foliar attributes. It was not until I flowered DJHM 13027 that I was able to identify Begonia flaviflora. The foliage is handsomely mottled if somewhat understated, though the large bright yellow flowers leave little doubt as to its identity. It has thrived in a bright spot of the woodland at Heronswood since 2014. Incredible India During two trips to the Mishmi Hills, far eastern Arunchal Pradesh, India, in 2016 and 2018, I was introduced to a mind-bogglingly rich flora including a cache of exciting begonias among many other taxa, including Brassaiopsis, Helwingia, Maianthemum, Paris, Podophyllum, Polygonatum, Primula, Rhododendron, Sarcococca, Schefflera and Styrax. As one begins the ascent to Mayodia Pass from the town of Roing, ultimately reaching an elevation of 12

Hardy begonias Fruit of Begonia silletensis (top) rise above the canes in August and September. in Arunachal Pradesh, India, and During our return to Mayodia from Anini in Begonia DJHAP 18087 (above). 2018, a roadside stop along the severe switchbacks dark purple in varying degrees. This collection, prior to the pass revealed a deeply dissected DH 16011, has proved to be perfectly hardy at Begonia (DJHAP 18087) with yellow flowers Heronswood Garden, producing startlingly pink in the heavily denuded embankments. Despite a flowers slightly above the foliage in August. concentrated effort to find more, only a total of two plants were observed with one seed capsule. At much lower elevations near Anini, 168km The road system here was favoured grazing for the of white knuckle driving from Mayodia Pass, two semi-domesticated cow-like mithun, and their enormously tall species were found growing side associated pest, a species of terrestrial leech. Even by side. Begonia roxburghii bears handsome, glabrous after decades of suppressing a distaste for leeches foliage along canes to 2.5m. Substantial numbers of and their habits, the quantities existing here set fairlly large flowers are produced at the nodes. The an entirely new standard. One individual required capsules are hard to distinguish from bulbils. Virtually removal from the inner lip of my traveling comrade. touching were similarly sized plants of what was believed to be B. acetosella. The smaller leaves have DJHAP 18087 is assuredly an undescribed a felted surface lightly stained with bands of species, some individuals possessing seductively brown, while terminal flowers of pink or white cut foliage, deep green above and red beneath. The nicely saturated yellow flowers are presented Digital taster edition in late summer at the same height as the foliage. I hope it will receive a name honouring its native locale or the people local to it. Seed sowing and garden growing With an estimated one million seeds per ounce, one seed capsule per collection is all that proves necessary in the field. Thoroughly drying the seed is of paramount importance and glassine envelopes should be favoured over statically-charged plastic to allow easy extraction of seed for sowing. Seed is sown uncovered on a soilless compost without cold stratification in a cool glasshouse, with the containers covered in plastic film to stabilize humidity. Artificial light is recommended. Over-sowing will lead to fungal infections as does stagnant air conditions once germination has occurred. Clonal selections are propagated without difficulty by stem, leaf blade or leaf petiole cuttings, or by bulbils in those species kind enough to offer them. Rooting hormones are ineffectual with any leaf tissues. As the collection of Begonia species has grown, with unknown or doubtful hardiness associated with some species, all are now preemptively and generously covered with dry cedar shavings in early November. Being hydrophobic by nature, the shavings protect from excessive moisture as well as moderating temperatures during arctic outbreaks. The shavings are carefully removed as early as mid-March when new growth has generally already commenced from the plants beneath. Daniel J Hinkley VMM is founder and Director Emeritus of Heronswood Garden. He has been awarded the 13

PHOTOGRAPHS CHRIS SANDERS The showy rowan Sorbus decora (above) is a species mysteriously Chris Sanders reflects on a rare mountain ash, unavailable in the Sorbus decora, and recommends it for the horticultural trade stocklists of enterprising nurserymen at present. FOR SUCH AN ornamental species, one sometimes accorded separate specific status as that well lives up to its name, Sorbus decora, S. groenlandica. For much of its range, it overlaps the northern or showy mountain ash is with the related S. americana from which it can surprisingly scarce in UK cultivation. It is not be readily distinguished by its shorter, wider and listed in the most recent RHS Plant Finder, nor blunter leaflets and larger fruits. In the wild it does it even find a place in The Hillier Manual inhabits montane forests and swamps from the of Trees and Shrubs. Fortunately, several wild alpine and sub-alpine zones down to rocky river collections are represented at Liverpool University’s banks and lakeside shores. Its size can vary from Ness Botanic Gardens, Wirral, on which most of a shrub to a tree to 10m high and it often grows the following observations are based. in poor, nutrient-deficient soils. Sorbus decora is native to north-eastern North The oldest trees at Ness were planted some America, extending from Labrador and Newfoundland 30 years ago and have formed fairly upright, east to Saskatchewan, then south through the pyramidal crowns, about 5–6m high. They are states of the Great Lakes region and New England, at their best from early August onwards when reaching as far west as Minnesota and Illinois in bearing remarkably large, heavy clusters of bright, the south. Populations from southern Greenland, deep scarlet-red fruit – a far more telling colour coastal Labrador and high mountain elevations are than those of our native rowan, Sorbus aucuparia. 14 The Plant Review

Sorbus decora Fruiting branches are bent under the weight of berries (above and above, left) which are carried between August and October. Sorbus decora will form a large shrub or small tree to 10m high in optimal conditions (left). The fruiting branchlets are bent down under the in the thin, acid soil over sandstone at Ness, where weight, thus causing some of the leaves to show average annual rainfall is about 750mm. No serious their paler undersides, a useful identification predator or disease problems have been observed. character. This splendid show usually lasts for several weeks until they are eventually devoured Between the years 1980 and 2000 an exceptionally by the Scandinavian thrushes in October. Finally, heavily fruiting cultivar of S. decora originating the leaves turn a pleasing orange-yellow to from the Netherlands and called ‘Grootendorst’ complete the season’s display. (presumably for Grootendorst Nursery) was grown Unfairly scarce and distributed by Bridgemere Nurseries, Nantwich, All the wild collections at Ness have been found Cheshire. This excellent tree seems to be no longer to be tetraploid apomicts (2n = 68), a relatively in commerce in the UK, but can still be found in unusual state among the orange- and red-fruited, parks and gardens, particularly in the midlands. pinnate-leaved Sorbus species (McAllister 2009). Some fine examples can be seen in Carmountside This means that seedlings will be genetically Crematorium, Stoke-on-Trent. As an apparent variant identical to the parent tree. Trees on their own of an apomictic species, its exact nature is uncertain. roots have proved to be quite drought-tolerant It is a great pity that this handsome, ornamental Digital taster edition rowan has become so scarce. It is very suitable for use as a street tree, in parks and other open spaces and especially in gardens where space is limited. Perhaps some discerning nurseryman will read this article and decide to make it available once again. Chris Sanders vmh is a member of the RHS Woody Plant Committee and is involved in several RHS woody plant trials as a forum member. Reference McAllister, H (2009) The Genus Sorbus, Mountain Ash and Other Rowans. RBG, Kew. 15

ROGER PARSONS Tricoloured Lathyrus × hammettii ‘Three Times as Sweet’ sweet peas between ‘Matucana’ and Lathyrus belinensis. Graham Rice looks at the latest Lathyrus The cross yielded about 100 seeds, mostly and finds good things come in threes poorly formed. In 2014 only two seeds out of 100 germinated, one died early but the IN 2020 THOMPSON & Morgan introduced other one reached flowering size. what was blazed as ‘the world’s first tricoloured sweet pea’. Developed at T&M’s ‘It had very unusual colouring, showing a typical own breeding station in Suffolk by Cory Cup- white and magenta stripe pattern, but with the winning breeder Charles Valin, the sweet pea back of the standard a deep purple, giving a world soon pointed out that, although an attractive tricolour effect to the whole flower. It has four new introduction, other tricoloured sweet peas had or five flowers per stem, and the scent is intense. already been introduced. There is, however, an interesting story behind the T&M plant. ‘This unique plant was selfed and proved more or less instantly fixed, with minor variations in Named ‘Three Times as Sweet’, referring neatly colour intensity and seed germination. I took it to its colouring and its sweet fragrance, T&M say to the F4 generation and it was then decided it was ‘the marbled blooms blend lavender-blue, burgundy stable enough to move it towards seed production. and white to create a truly eye-catching display.’ ‘Genetically it is quite a mysterious phenomenon Charles Valin explained the background, which as the first hybrid seen in 2014 could not be a self also reveals something of the surprises that can from ‘Matucana’ but there was no obvious occur when developing new plants. contribution from the male parent (L. belinensis) either. Keith Hammett in New Zealand had a ‘This plant came from a cross made in 2013 similar experience with his ‘Enigma’’. 16 ‘Three Times as Sweet’ is, basically, a stripe but derived separately from all other striped sweet peas’. Charles suggests that the most likely explanation for an instantly fixed (non-segregating) hybrid is that the interspecific crossing triggered the activation of an existing transposon (jumping gene, as in multi-coloured corn, Geranium pratense The Plant Review

Tricoloured sweet peas GRAHAM RICE of Leucanthemum × superbum, the Shasta daisy, by the groundbreaking American plant breeder Luther Lathyrus × hammettii ‘Ella Mountbatten’ Burbank. He reported that his first work involved crossing wild British and Pyrenean Leucanthemum ‘Striatum’ and striped Antirrhinum cultivars). The species, crossing the result with a Portuguese activated transposon created a mutation where it species and then crossing the result of that exited or re-entered the ‘Matucana’ DNA. This hybridization with the November-flowering point mutation is responsible for the novel colouring. Japanese Nipponanthemum nipponicum. The weird world of wide crosses The other most recent tricoloured variety, ‘Ella There is no dispute that he made all these Mountbatten’, was developed by Roger Parsons crosses, and that his plant represented a significant and shares distant ancestry with ‘Three Times as step forward. But there is no evidence of any Sweet’ in having L. belinensis in its background. Nipponanthemum genes in the wide variety of Shasta ‘‘Ella Mountbatten’ arose from a cross I made in daisy cultivars now grouped under L. × superbum. 2008 between a white Spencer seedling and ‘Erewhon’,’ Tricoloured sweet peas Roger told me. ‘‘Erewhon’ has L. × hammettii There have been previous tricoloured sweet peas (L. belinensis × L. odoratus) ancestry so technically and these include, in order of introduction: ‘Ella Mountbatten’ is also L. × hammettii.’ ‘Senator’ A purple and maroon Grandiflora flake This whole area of interspecific and intergeneric with white standards flaked in maroon, and white pollinations triggering unexpected apomixis (seed wings flaked in purple (Henry Eckford, 1891). formation without fertilization) has been investigated by Julian Shaw of the RHS in relation to the ‘Fire and Ice’ A modern Grandiflora with white recently claimed hybrids between Aeonium and standards, flared in crimson, and white wings Sempervivum. He could find no evidence of shading to blue at the edges (Mark Rowland, apomixis, both the F1 and the F2 generation are 2005). The colouring of ‘Fire and Ice’ was later quite variable, but these plants have changed his incorporated into the dwarf Cherub Series as perception of intergeneric hybrids and he no longer ‘Northern Lights’. expects intermediate appearance. ‘Enchanté’ A tricoloured Spencer, the standard The example of intergeneric pollinations is cherry pink with a large white base with pencil triggering unexpected apomixis that always markings, while the wings are a soft mauve (Keith comes to my mind is the original development Hammett, 2009). Graham Rice writes the New Plants blog on the RHS Digital taster edition website and his own Graham’s Garden blog. Acknowledgements I would like to thank Charles Valin (now Breeding Director at Valin Genetics); New Zealand plant breeder Keith Hammett; Julian Shaw, International Orchid Registrar; and Roger Parsons, co-author of Lathyrus: The Complete Guide, for their help with this article. Reading Lathyrus The Complete Guide is the definitive book to all 150 species and 500 sweet pea cultivars, by Roger Parsons and Greg Kenicer. Available from RHS mail order (rhsshop.co.uk), price £40. 17

The loveliest of pines Harry Baldwin runs an appreciative eye over the patchwork colours of lace-bark pine P INES ARE OFTEN grown for their slender Introduction to the West habit, sometimes their long fine needles or Pinus bungeana was discovered in 1831 by their decorative cones, but almost never for Alexander von Bunge, for whom the species is their bark. An exception is Pinus bungeana, also named. A naturalist, he had been sent to Beijing known as lace-bark pine or white pine, one of the (then Peking) by the Russian government. While most striking species of the genus. Its exfoliating staying at a Buddhist monastery he encountered bark flakes off in patches to reveal a mosaic of problems with the Chinese authorities and was creamy yellow, steel blue, grey and buff brown forbidden to leave the city. It was during his which become pure white with age. Alongside two confinement that he came across Pinus bungeana other Asian species, P. gerardiana and P. squamata, and Catalpa bungei for the first time. Growing in this feature is also displayed in unrelated taxa, the grounds of temples across Beijing, these are such as Cornus wilsoniana, Platanus and Stewartia. just two of many plants he encountered that were But in my opinion this character is never so previously unknown to Europeans. decorative as in this species, whose combined attributes constitute a remarkable ornamental tree. It was not until 16 years later that P. bungeana was described by Joseph Zuccarini in Endlicher’s Unlike most other pines, the trunk of P. bungeana Synopsis Coniferum. The exact location of the divides low to the ground, sending up a number of species was not cited but the name ‘Kiu-lung-mu’, branches and forming a graceful, wide crown. Its which translates as ‘nine dragon tree’, was stated. needles, held in tight fascicles of three, are dispersed This was not the Chinese common name of the thinly among the canopy, allowing its bark to ‘sparkle species as once believed, but a name given in the with light’. This poetic description by Chinese author 18th century by a Chinese emperor, Qianlong, to Chen Yung (1937) may offer some explanation an individual specimen. This specimen still grows as to why it is so commonly planted in places of in the courtyard of Chieh-tan-szu Monastery in Chinese worship but does nothing to explain west Beijing, and is likely to be the tree from which why it is so little seen in cultivated collections. was taken the type specimen. Male cones of Pinus bungeana (left) appear above the stiff needles; the paint-by-numbers bark (right) for which the species is prized. 18 The Plant Review HARRY BALDWIN WILLIAM FRIEDMAN

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PLANT 15m >| DOWNLOAD |< |< 7.5m >| Distribution North China from Shangdong to northern Sichuan Habitat Mountains with hot summers and cold winters Conservation status Least concern Hardiness H7 Bunge makes no note of his acquaintance with HARVARD UNIVERSITY ARCHIVE the nine dragon tree or the species in general; its beauty remained unknown to the West until The nine dragon tree, which grows to this day Robert Fortune collected material for the first time in Beijing, in a picture taken by Frank Meyer. in 1846 and sent small trees to England. plates, revealing a mosaic of creamy yellow, steel- Later, in 1861, Fortune observed old specimens blue-grey and buff-brown. With age, the colours in and around the old city of Peking. He offered his begin to blend to a bright chalky white, a dazzling personal account of these trees in his book, Yedo sight when the sun’s rays reflect off its white- and Peking (1863), accurately portraying their washed stems. One may say the planting of this peeling bark and their distinctive branching habit tree is the ultimate investment for the next and providing the first illustration of the species. generation, as this transformation does not take Native distribution place for 75–100 years. Since Fortune’s account, there have been numerous reports of the species around Beijing, though few Elwes and Henry in their Trees of Great Britain of these accounts detail wild populations. Truly wild and Ireland, printed in 1906, 60 years after the trees were first recorded by Augustine Henry in introduction of P. bungeana, stated, ‘no trees in 1887, followed by Frank Meyer in 1907, and Ernest cultivation are as yet old enough to show the Wilson and Harry Smith in 1924. Each describe beautiful white bark which renders this pine so the vast quantity being sold at market stalls, as remarkable at Peking’. This is echoed in 1988 in well as the demand for the properties of its timber. an article by Richard Nicholson in Arnoldia when he asks why there are still no pines in cultivation Despite having a wide distribution in northern presenting the white bark. Perhaps the closest one China, the native range of the species is hard to may get to seeing this effect in cultivation, is by determine due to it being widely planted for many observing the champion tree at Royal Botanic hundreds of years. It is known in Chinese literature Gardens, Kew. It was planted around 1860 and still from as early as the Ming dynasty (1368–1644). displays coloured bark, but with white starting to It is stated in the Gazetteer of Shang-chou that the dominate. It remains a mystery what stimulates white pine existed in the hills around the capital this white colour or prevents its production. in their thousands. Although all trees in Beijing are Perhaps it requires higher levels of ultraviolet light planted, Beijing sits within the natural range of the than in the UK, a limestone substrate, or maybe trees species and it is quite possible that extensive forests in Western cultivation are still just too young. existed in the area at the time of the Ming dynasty. Kaleidoscope bark The Plant Review The most celebrated and striking feature of this species is its bark. Unlike other members of the genus, bark of P. bungeana exfoliates in papery 20

Pinus bungeana ROYAL BOTANIC GARDENS, KEW ARCHIVE HARRY BALDWIN Pinus bungeana has long had an important The champion tree at Royal Botanic Gardens, Kew, place in Chinese art and culture. is taking on the white stems of mature specimens. Germinating and growing an ideal candidate for many parks and gardens, Cultivated specimens of Pinus bungeana are especially in urban areas. generally few and far between in Europe and North America and tend to be confined to It is clear that for thousands of years this pine botanical collections. Being such a slow-growing has caught the attention and the imagination of pine discourages the commercial sale of this writers, poets and plant collectors, and has become species, hence its low profile. Growing from seed a notable symbol of many spiritual communities in can be time-consuming, as germination can often China. It is inspiring to think of the small sapling be slow, sometimes taking in excess of two months beginning life high up in the mountains of China after stratification. In the first year, seedlings will being planted in the grounds of a temple or other scarcely attain a height of more than 2–3cm. place of worship, bearing witness to burials and ceremonies, weathering snow storms and enduring Growing young specimens in free-draining drought. Similarly, we can picture other young media such as perlite and sand with a low-nutrient plants crossing the oceans and continuing life in compost is key to survival. After the first year, the Western gardens. Every plant has a story to tell seedling will begin to form lateral branches and and I hope some of those reading this article might these will quite quickly outcompete the terminal be moved to try to grow this fascinating and bud. As a result, a bushy habit is quickly established charismatic species themselves. which later matures to a multi-stemmed tree. Harry Baldwin is a dendrologist and horticultural taxonomist at Royal Botanic Gardens, Kew. One must bear in mind good drainage, but the Chen, Y (1937) Illustrated Manual of Chinese Trees species is generally very cold-tolerant and easy to and Shrubs. Nanking. Elwes, H & Henry E (1906) grow. However, a warm and sheltered spot will Trees of Great Britain and Ireland. Privately printed, allow it to put on good growth more quickly. Edinburgh. Fortune, R (1863) Yedo and Peking. John Growing at high altitudes in northern China, the Murray, London. Nicholson, R (1988) A ghostly pine. species is exposed to harsh climatic conditions Arnoldia 48(2): 33–38. year-round, experiencing icy-cold winters with high winds and long, hot, dry summers, making it 21 Digital taster edition

ON TRIAL Persicaria chinensis var. ovalifolia ‘Indian Summer’ Rosalyn Marshall investigates the past, assesses the present and relishes the promising future of an appealing Persicaria PERSICARIAS ARE A diverse group of entries showed strength and vigour, and which plants in the Polygonaceae, or knotweed remained disease-free. Persicaria chinensis var. family. They include mixed border stalwarts, ovalifolia ‘Indian Summer’ stood out among the rock garden specialists and foliage favourites. 93 entries for its bushy habit and masses of Recent name changes separate these distinctive unusual, late-season flowers. groupings into different genera (Edwards 2022) What’s it like? but Persicaria sensu lato (as it was previously Persicaria chinensis var. ovalifolia ‘Indian Summer’ recognized) was trialled at RHS Garden Wisley is clump-forming with many thick, upright stems. from 2019 to 2021. The objective of the trial was to Bearing evenly-spaced, evenly-sized leaves, it has recommend the Award of Garden Merit (AGM) to a pleasingly tidy habit and in the third year of the entries that met the judging criteria and will trial reached 1.2m tall. Its leaves are glabrous and perform reliably as garden plants. The trial rounded, marked at first with a faint chevron that assessment forum looked at the length of flowering disappears as the leaf matures. Through summer period, the foliage effect of some plants, which 22 The Plant Review

RHS Trials PHOTOGRAPHS BY ROSALYN MARSHALL Wickenden’s collection was one of the first introductions of this species to cultivation in ‘Indian Summer’ in trial (left); a source of late nectar the UK. There have been at least two others from (top); the broad leaves are an attractive feature (above). different areas of its range: another Wickenden introduction, P. chinensis var. hispida MCW 29, and into autumn a deep reddish purple flush collected from Myanmar; and Polygonum chinense spreads across the leaf surface, more strongly in BSWJ 11268 introduced by Crûg Farm Plants from sun. Small, round clusters (corymbs) of flowers are Sumatra in 2005, again identified as Persicaria held on red, glandular-hairy, branched stems. The chinensis var. ovalifolia by Shaw (pers. comm). small pink flowers sit within red bracts and are Possibilities for planting late into bloom. In the trial it began flowering at With its bright pink flowers and autumn leaf the end of July and carried on until the first frosts. colour, ‘Indian Summer’ is luminous on the dullest Shining black berries follow the flowers, but these autumn day. Its rounded foliage and habit, and its were only occasionally produced. It proved to be unique flowers lend brilliance to exotic plantings. hardy on the Trials Field, but can be frost- It will grow in well-drained, moist soil in sun or susceptible when grown in a pot. part to full shade where conditions do not become hot and dry in summer. The first frosts will kill off A case of identity the foliage and stems can then be cut back to the ‘Indian Summer’ was collected by the late Michael ground. Slowly spreading by short rhizomes, it Wickenden of Cally Gardens from Mishmi Hills in can easily be divided. The whole Persicaria trial Arunachal Pradesh, north-east India in the 2000s. attracted a variety of pollinators, and ‘Indian It was first offered in his catalogue as Persicaria sp. Summer’ was particularly attractive to honey Mishmi Hills, and then identified as P. chinensis bees over its long flowering season. var. ovalifolia by Julian Shaw (pers. comm.). A split in the genus Persicaria chinensis var. ovalifolia is native to India, Persicaria has been the subject of a recent review, east to south-central China and Japan, and south based on molecular and morphological evidence, to Sumatra. It is also a weedy species where it has which has seen the genus split. The trial was been introduced to climates without hard winter mostly comprised of P. amplexicaulis cultivars frosts, such as La Réunion Island, Jamaica, Hawaii which have now been transferred into Bistorta and New Zealand (CABI 2022). along with P. affinis. Some of the most different plants in the trial, with panicles of white flowers, It commonly has white or pink flowers and a such as P. alpina, are now included in Koenigia. scrambling habit and is one of three varieties of However, P. chinensis var. ovalifolia remains in P. chinensis (var. hispida, var. ovalifolia and var. Persicaria along with others grown for foliage, chinensis) accepted by Plants of the World Online. including P. filiformis and P. microcephala. Digital taster edition The total number of AGMs in Persicaria increased from six to 33 following the trial (only quickly to be dispersed among three genera – Persicaria, Bistorta and Koenigia), including P. chinensis var. ovalifola ‘Indian Summer’. Download the trial report at rhs.org.uk/plants/trials-awards/. Rosalyn Marshall is a Trials Officer at RHS Garden Wisley. Acknowledgements Many thanks are owed to Julian Shaw and Ben Probert for their help gathering information about this cultivar and its introduction. References CABI (2022) Invasive Species Compendium. www.cabi.org. Edwards, D (2022) Plant names bulletin. The Plant Review 4(1): 58–61. 23

Boquila The Plant Review trifoliolata: a mysterious shape-shifter Ernesto Gianoli hunts out an astounding botanical chameleon IHAD BEEN WORKING in the temperate rainforest of southern Chile for years, studying plant ecology. Field visits were always on a tight schedule, each day packed with plant measuring and species sampling. Then, one day, I felt with this routine we were partly missing the pleasure of observing nature. I recalled that the naturalist’s view (observation) should come first, and the scientific approach (understanding) should follow. I decided to take the afternoon off and dedicate some hours to walking in the forest, just observing. And then it happened. A moment’s observation that resulted in a ground-breaking and baffling discovery. I was puzzled why some leaves of a particular shrub were growing from much thinner stems than others. I then realized that the stems belonged to two different species: one a shrub and the other a twining vine (Boquila), but the leaves were strikingly similar. Immediately I started to seek other Boquila vines, attached to other tree species, and found that this mimicry was very common. It was astonishing. I was familiar with the vine, but I had not noticed this feature before. Back in the lab, I asked people to send me their Boquila pictures and there it was: in about three- quarters of the cases Boquila was quite similar to the closest leaf from another tree or shrub. The plant with a difference Boquila trifoliolata, a twining woody vine endemic to the rainforest of southern South America, is the only species in the genus Boquila from the family Lardizabalaceae. It looks just like any woody vine in a forest where lianas thrive, but it is far from ordinary. In his National Geographic blog, Robert 24

Boquila PHOTOGRAPHY BY ERNESTO GIANOLI Boquila leaves mimicking hosts (opposite, the spiny leaf margins of the model vine (Gianoli top to bottom): Aextoxicon punctatum, 2017). Botanical descriptions of Boquila do not Myrceugenia planipes, Mitraria coccinea, mention spiny leaf tips or spiny leaf margins. Amomyrtus luma, and Ranunculus repens (top) and Rhaphithamnus spinosus (above). Unpublished observations in the same forest Krulwich dubs it ‘arguably, the most mysteriously reveal other mimicry tricks by this unique vine. talented, most surprising plant in the world’. Why? When entwined around a tree with opposite leaves Mimicry in plants is not common, but happens distinctively forming a given angle, Boquila changes (Barrett 1987). However, other accounts of plant the otherwise flat aspect of its leaf lamina in such mimicry always involved specific, one-to-one a way that the tree’s leaf angle is imitated. However, relationships between the mimic and the model, its mimicry is not boundless. For instance, serrated with similarity shaped over evolutionary time. leaf margins are particularly difficult to copy and, Boquila rewrote the books on plant mimicry. It in such cases, Boquila does its best and attains is able to mimic well over a dozen species, even a limited resemblance by producing some leaf without direct contact (Gianoli & Carrasco-Urra indentations (Gianoli & Carrasco-Urra 2014). 2014, Gianoli 2017). Strikingly, a single individual The overall success rate of leaf mimicry observed vine can mimic two different tree species when in the field, including all paired associations, crossing from one plant to another. Moreover, ranges between half and three-quarters. trailing Boquila vines in the forest understory are Elusive explanations able to mimic an exotic herb (Ranunculus repens) We currently lack a mechanistic explanation for introduced a few decades ago (Gianoli 2017). this mimicry. We might hypothesize that host- plant volatiles trigger specific phenotypic changes Leaf mimicry by Boquila has been characterized in neighbouring Boquila leaves. However, research in terms of leaf size, shape, colour, leaf angle, on airborne plant-to-plant signalling has not petiole length and spininess (Gianoli & Carrasco- reported specific morphological changes in leaves. Urra 2014). The latter feature deserves further description. Boquila can develop a small spine at its An alternative hypothesis, but perhaps less leaf tip when close to species with such mucronate plausible, would involve horizontal gene transfer leaves, e.g. Luma apiculata and Rhaphithamnus between plants, a phenomenon that is increasingly spinosus. Further, when close to the vine Cissus reported. These cases are thought to be mediated striata, Boquila may produce five spiny tips in the by a vector, or result from plant parasitism or margin of each of its three leaflets, thus mimicking natural grafts. The plasticity in leaf mimicry in B. trifoliolata could involve horizontal gene transfer Digital taster edition mediated by airborne microorganisms. The latter speculation is based on the fact that mimicry is observed with respect to the foliage to which the vine is nearest, irrespective of whether this foliage belongs to the host tree that the vine has climbed. Interestingly, a recent study found that endophytic bacteria in the leaves of Boquila are associated with the mimicry pattern (Gianoli et al. 2021) Ernesto Gianoli is a botanist at Universidad de La Serena, Chile, interested in the functional and evolutionary ecology of plants. Suppliers Burncoose Nurseries, Crûg Farm Plants References Barrett, SCH (1987) Mimicry in plants. Sci. Amer. 257: 76–85. Gianoli, E (2017) Eyes in the chameleon vine? Trends Plant Sci. 22: 4–5. Gianoli, E & Carrasco-Urra, F (2014) Leaf mimicry in a climbing plant protects against herbivory. Curr. Biol. 24: 984– 987. Gianoli, E et al. (2021) Endophytic bacterial communities are associated with leaf mimicry in the vine Boquila trifoliolata. Sci. Rep. 11: 22673. 25

Thinking outside the phlox Birgitte Husted Bendtsen recounts the story of a moment in plant breeding that has left a long legacy in gardens COURTESY OF ANJA MAUBACH arendsii. Arends had achieved his goal and the plants started to flower in late May. There were 10 M OST GARDEN PHLOX, cultivars of cultivars, all given girls’ names, but due to bombing Phlox paniculata, flower from around during the Second World War only P. × arendsii July until early autumn. However, ‘Lisbeth’ and P. × arendsii ‘Hilda’ have survived other species are spring flowerers, one important to the present day. The cultivars of P. × arendsii example being P. divaricata. introduced in more recent decades are backcrosses of original cultivars with P. paniculata. Georg Arends (1863–1952), a nurseryman based Keep the insects out of it in Wuppertal-Ronsdorf, Germany, had the brilliant Improvement of straight Phlox paniculata also idea of crossing the two species to produce a hybrid claimed Arends’ attention. His aim was to create that he hoped would flower over a very long period. cultivars with very brightly coloured flowers that didn’t fade in the sun. He made his first attempts in around 1906 when he managed to make P. divaricata flower for a Another German, Karl Foerster (1874–1970), is second time in order that he could have flowers well known for his many phlox cultivars, but in his available for pollination when the earliest cultivars breeding methods he was the complete antithesis of P. paniculata began blooming. Unfortunately, of Arends. Foerster raised thousands of seedlings however, the pollination of P. paniculata by in hope of achieving maximum variability and thus P. divaricata did not give rise to seed. increasing the chance that one of the plants might have the sought-after traits. Contrary to this, However, the following summer he also made Arends often had success with only a few seedlings the reciprocal cross and was successful in gaining as his crosses were always meticulously planned seed from P. divaricata. with interference from insects assiduously avoided. An inspection of the flowers revealed to Arends Among Arends’ garden phlox still available that the stigma of P. divaricata is very close to the are the following: ‘Septemberglut’ (1918, blood ovary whereas the stigma of P. paniculata sits on red), ‘Albert Leo Schlageter’ (1925, bright carmine a long style. He conjectured the pollen from red) and ‘Paul Hoffman’ (1925, dark purple). P. divaricata couldn’t make long enough tubes to Early attempts at phlox hybrids reach the ovary of P. paniculata and fertilize it, a Arends had previously tried to cross P. paniculata theory that was proved correct many years later with both P. maculata and P. glaberrima. However, by Plitmann and Levin (1983). both crosses failed. When he used P. carolina A star is born instead of P. paniculata as the male parent, the In 1912 and 1913 Georg Arends launched the first pollinations led to fertilization. Both P. glaberrima batch of his hybrid phlox, which he named Phlox and P. maculata produced seeds and Arends 26 introduced the progeny as P. glaberrima hybrids The Plant Review

Arends’s phlox Raised by Georg Arends (opposite), Phlox × arendsii is a ‘Ronsdorfer Schöne’ is hybrid of P. divaricata and P. paniculata. Only ‘Hilda’ (left) a low-growing cultivar and ‘Lisbeth’ (right) survive of the original crosses. bred by Georg Arends using Phlox douglasii. ‘Alpha’ (above), and P. maculata hybrids. ‘Schneelawine’ (right) Only the latter are still with us, listed as cultivars and ‘Rosalinde’ (above right) are hybrids of of P. maculata: ‘Alpha’ (1912, lilac-rose), ‘Rosalinde’ Phlox maculata. (1918, pink) and ‘Schneelawine (1918, white). Phlox for the rock garden ‘Albert Leo Schlageter’ Arends had very good contacts in England having (above), ‘Paul Hoffman’ worked in Tottenham from 1885 to 1886 and made (right) and ‘Septemberglut’ the best of his learning opportunities during his (below) are Arends stay. In his spare time he visited parks, RHS shows selections of Phlox and Royal Botanic Gardens, Kew at least once a paniculata. month. He was especially interested in the Rock Garden at Kew, which probably led him to build a Digital taster edition rock garden years later at his nursery in Ronsdorf. In 1914 Arends got a special rock garden plant from England, the true P. douglasii, which he found very pretty but extremely difficult to propagate. By crossing this with other cultivars, he finally produced a good plant that resembled the species but was easy to propagate. It was introduced in 1927 as P. douglasii hybrida. In 1968 his grand- daughter rechristened it P. douglasii ‘Georg Arends’. Other low-growing phlox bred by Arends are P. subulata ‘Maischnee’ (1927, white) and P. subulata ‘Ronsdorfer Schöne’ (1931, bright pink). The nursery today Usually an account of an old famous nursery ends with ‘The nursery has long gone’! Luckily this does not apply to Arends’ nursery, which is today run by his great-granddaughter Anja Maubach. Birgitte Husted Bendtsen lives and gardens in Denmark and is author of a monograph on Phlox. Reference Plitmann, U & Levin, DA (1983) Pollen- pistil relationships in the Polemoniaceae. Evolution 37: 957–967. 27

FHF GREENMEDIA / GAP Notable Rosa x centifolia cultivars include heavily mossed ‘Cristata’ (syn. ‘Chapeau de Napoléon’) (above) and sultry purple ‘Nuits de Young’ (below). Sterling Moss NOVA PHOTO GRAPHIK / GAP HOWARD RICE / GAP For quality and fragrance, the first Moss rose, Rosa x centifolia ‘Muscosa’ (left), is difficult to surpass. David Stone discusses some And yet these are relative newcomers to the historic Moss roses that have given world of historic roses, boasting a mere 270 years excellent service over the years of cultivation. But such is the agelessness of their charm that one may be forgiven for believing that FEW GROUPS OF roses can better kindle a they have graced our gardens since time immemorial. glow of nostalgia into a flame than the Moss The original Moss roses. Beloved of Victorian gardeners, redolent The first Moss rose was discovered, probably of old English cottages in June and entwined with in France, in the mid 18th century. It arose as the elusive fragrances of yesteryear, when we were a natural mutation, or ‘sport’, of Rosa × centifolia, young and summers lasted forever. A Moss rose. Provence rose, which itself had only appeared 100 Could any other flower conjure so many memories years earlier. Rosa × centifolia, (‘the rose of a of times that seldom were? Probably not. hundred leaves’ or, more correctly, petals), was a chance hybrid discovered in Holland in 1650 and 28 The Plant Review

Historic roses DAVID STONE HOWARD RICE / GAP Rosa x centifolia ‘Shailer’s White Moss’ (syn. ‘Muscosa Alba’) and R. x centifolia ‘James Veitch’. immediately valued for the unrivalled fullness and when touched, freely transfer their musky fragrance fragrance of its bright pink blooms. Nothing like to the finger. Furthermore, this mutation extended them had ever been seen before. In shape these to the sepals of the buds themselves, transforming blooms were almost globular, and their tightly these normally hard shells into crested fronds of packed petals were likened to the rather blowsy fern-like beauty and moss-like softness. Thus, cabbages of that era. Hence the name cabbage a freshly opening flower bud may appear to be rose was born, and has remained ever since. embraced by a filigree of green fernery, presenting a ready-made buttonhole of quite exquisite charm. Rosa × centifolia itself forms a rather angular shrub, its prickly branches often zig-zagging across The Victorians took this rose to their hearts, each other as if uncertain of which direction to and most of its many hybrids were raised and take. Its advent on the gardening scene heralded introduced in the thirty years following the young the elevation of the rose from the attractively Queen’s accession to the throne. These include old utilitarian to the purely ornamental. It is sometimes favourites such as the old velvet moss rose, ‘William difficult to remember that, until the late 1700s, Lobb’ (1855), the very graceful, bright crimson gardens devoted solely to the cultivation of roses ‘Henri Martin’ (1863), the purplish crimson for the beauty of their blooms were a very rare ‘Capitaine John Ingram’ (1856) and the dark phenomenon indeed. maroon-purple ‘Nuits de Young’ (1851). Credit for this elevation in status is generally Elegant and intensely beautiful as these cultivars given to Josephine, wife of Napoleon Bonaparte. are, few surpass the old common moss in the It was in the extensive grounds of her chateaux quality, fragrance and captivating beauty of their at Malmaison that she developed a garden solely flowers or the intensity of their mossy stems. Cup devoted to the visual beauties of roses. It is claimed a bloom of ‘Muscosa’ in yours hands and drink every cultivar of rose then known to be cultivated deeply of its fragrance; the spicy scent of its moss in Europe was gathered at Malmaison. Notable will remain on your fingers long after that of the among these was Rosa × centifolia, and its several bloom has left your mind. naturally arising sports and offspring, including the very first Moss rose, R. × centifolia ‘Muscosa’. In keeping with most historic roses, ‘Muscosa’ By any other name blooms in midsummer. To retain an open shrub, It is, perhaps, unfortunate that this superb cultivar crossing branches should be pruned back in winter should have been called common moss, for there when new, strong shoots of the current year’s is little that is ‘common’ about this extraordinary growth may also be reduced by as much as one rose. I have written that R. × centifolia is a particularly half. As the flowers produce no heps, spent blooms prickly plant, its spines extending to the calyx of may be removed as soon as they have faded. the flower bud itself. But in the Moss roses, these prickles have been transmuted, by the artful hand David Stone was Head Gardener at Mottisfont Abbey of Nature, into softly felted scent glands which, for 38 years and is an RHS Associate of Honour. Visit Historic Roses Group: historicroses.org Digital taster edition 29

Philadelphus ‘Casa Azul’ Jim Gardiner reviews a fragrant foundling that has passed its mock-orange exams W HEN ASKED WHICH scented JIM GARDINER Philadelphus to recommend planting in gardens, the Lemoine and other JIM GARDINER Bubblegum- modern hybrids continue to be the sought-after scented flowers group. Philadelphus ‘Beauclerk’, P. ‘Manteau of Philadelphus d’Hermine’ and P. ‘Sybille’ are three of my favourites ‘Casa Azul’ with the July-flowering Philadelphus insignis worthy (above). The of wider recognition. However, in recent years, the shrub can be richly scented Philadelphus maculatus ‘Sweet Clare’, kept to size by a garden-worthy selection introduced by Maurice pruning (left). Foster, has made its mark. But to see it at its best you really need to plant it in an elevated position modules containing a conventional cuttings compost to take advantage of its nodding flowers. under mist or in a closed case. On a visit to Pan Global Plants, Nick Macer Philadelphus ‘Casa Azul’ can be grown with a showed me a plant that he found growing close variety of complementary plants, including spring to several Mexican species including Philadelphus bulbs and sub-shrubby salvias such as Salvia maculatus ‘Mexican Jewel’, P. palmeri and P. ‘Rose ‘Jezebel’ and S. ‘SoCool Pale Blue’ which extend Syringa’. Having a ‘powerful bubblegum scent’, the flowering season through to late autumn. Macer assumed it was a seedling of P. maculatus ‘Mexican Jewel’ which has a similar scent. He went Jim Gardiner vmh is a former RHS Director on to name it ‘Casa Azul’. of Horticulture. Philadelphus ‘Casa Azul’ is a first-class deciduous The Plant Review shrub for gardens of all sizes, provided it has a sunny site and is planted close to a path where its superb scent can be appreciated. Tolerant of all soil types, it blooms throughout June with an abundance of ‘look you in the face’, cup-shaped, pure white flowers with a purplish pink stain at the base of the petals. The lanceolate green leaves, paler on the underside, are on arching stems, thus giving a degree of compactness to the overall shape of the plant. By pruning immediately after flowering, the size of the plant can be managed depending on the space available. Being planted in a confined space, I have limited its height and spread to 1.5m, however this can be greater. I have not been able to thoroughly test its hardiness but consider it to be H5 (-15 to -10°C). ‘Casa Azul’ is plant predator and disease free. Propagation is by softwood cuttings taken when pruning. These are rooted by direct-sticking into 30

Planting MAURICE FOSTERAsperae, changing its name to Hydrangea an idea platyarguta. This is a morphological absurdity. It is hard to imagine two Maurice Foster asks should more be done plants so morphologically divergent, and to reconcile good taxonomic practice it appears to hold gardeners’ use value at with the needs of gardeners? zero. In the same study, eight morphologically distinct genera have been dumped SHOULD A BETTER balance be made between into Hydrangea. Hydrangea taxonomy becomes a botanical accuracy and the empirical mile wide and knowledge of non-botanical consumers such an inch deep. as horticulturists? With the advent of the Studies based on genetic data are no guarantee interpretation of laboratory data and its use as of durability or reliability, either. Just a year after an overriding element in determining taxonomic the Hydrangea study above, further work rescued issues, changes to genus and species names have some of the sunk genera. This resulted in proliferated in recent years. Botanists interpret H. involucrata and H. sikokiana being placed into the data in the interests of perceived technical the resurrected genus Platycrater, and H. paniculata accuracy, which can produce unsatisfactory going into H. heteromalla. The data are not outcomes for end users other than botanists. infallible, and are subject to rival interpretation. A higher purpose? Horticulturists are scarcely represented at the Botanists in the laboratory may say that they table to offer a practical point of view based on are looking to group plants that are most closely morphology and ecology, with which molecular related, and molecular analysis is the most phylogenetics could be combined. Increasingly, powerful tool for that purpose. But it is only outcomes seem weighted against gardeners. one tool: there are others that should also be Because scientific reputation is a significant factor considered to help long-term taxonomic stability. in reinforcing acceptance of taxonomic change, Botanists also say that molecular classifications use value is rarely questioned. can reflect predictability in horticultural areas such as plant breeding, disease resistance, and A typical example of imbalance is the sinking graft compatibility. This has, surely, to be tried of Michelia, Manglietia, Parakmeria and other in the field, empirically. With that in mind, this magnoliaceous genera into Magnolia. This change summer I will attempt a cross between Platycrater is based exclusively on genetic rather than arguta and Hydrangea aspera both ways, and the morphological evidence. The loss of horticultural results will be reported in due course. clarity is real. As a garden newcomer in our run of Parting ways milder winters, Michelia has become an important Is taxonomy now fully locked in the molecular ornamental genus, with many desirable species for phylogenetic laboratory with no regard for cool temperate gardens. It has a clear set of morphology, habitat or ecology? If so, might morphological characters that distinguish it from gardeners ignore these changes? There is no legal Magnolia. The two most obvious are that all plants requirement for their adoption, and general usage are evergreen, and they bear their flowers in the in the end will likely decide the issue. There may leaf axils rather than terminally. Most michelias well be a parting of the ways, with gardeners are not reliably hardy in cold gardens, useful sticking with Mahonia and botanists moving to knowledge already associated with the name. Berberis, or gardeners with Rosmarinus and botanists Submerging Michelia into the multiplicity of to Salvia, or gardeners with Michelia and botanists Magnolia means a loss of significant information. to Magnolia? If so, this is unlikely to be in the long- How stable is it? term interests of nomenclatural stability. There are plenty of other examples of the tyranny It was baseball player Yogi Berra who said when of the laboratory. For example, in Hydrangeaceae, you reach a fork in the road, ‘Take it’. I once asked recent work has removed dense, compact an eminent botanist whether taxonomy was an art Platycrater arguta into, of all places, section or a science. He thought for a while, then replied ‘Yes, it is’. Digital taster edition 31

INGO KACZMAREK HAGEN ENGELMANN UWE KERSTEN Contesters for the crown: from left to right, candidates 1, 2 and 3. Will the real to ‘Violet Queen’ receiving a Certificate of Merit ‘Violet Queen’ at the flower bulb assessment in Haarlem on 13 please arise? September 1926 as a new introduction from Van Meeuwen & Zonen. It was denoted ‘seedling no 97’ Wim Boens takes on the task of tracking and described as ‘single coloured, with violet down a genuinely regal naked lady reflexion’. In the following year the previous year’s With the publication of the wonderful new RHS accolade was elevated to Certificate First Class. monograph on colchicums (Grey-Wilson et al. Thanks to Johan’s research it is now clear this 2020) it became clear an important, historical cultivar was named and marketed by Van Meeuwen cultivar has been lost for some time. Neither the & Zonen in 1926 and it seems plausible it was one RHS Colchicum Trial of 1996 at Fellbrigg Hall nor of the seedlings sold off by Zocher & Co. The of 2014 at Hyde Hall was able to locate the real ‘large, double flowered lilac pink’ from the Zocher Colchicum ‘Violet Queen’. This has spurred some sales advert must be ‘Waterlily’ which was also plant enthusiasts in Germany to embark on a marketed for the first time by Van Meeuwen in 1926. quest to find this cultivar which may still grow unrecognised in old gardens. Two lithographs of ‘Violet Queen’ were What we know published at the beginning of the 20th century. The origin of this cultivar is not certain. It was The earliest is one by Van Meeuwen & Zonen, understood ‘Violet Queen’ was introduced by possibly published in 1928. It clearly shows a dark Zocher & Co. (closed in 1918) of Haarlem, the pink or violet, tessellated flower with a striking Netherlands, between 1900 and 1905. But white stripe on the tepals. The second was drawn International Bulb Registrar, Johan van Scheepen, in 1937 by Esther Bartning and published was unable to confirm this from the catalogues of in Foerster (1938). This shows a characteristic Zocher & Co. from the period. A possible lead is not visible in the other lithograph: a white stripe the sale of a batch of unnamed seedlings in 1917, clearly visible on the underside of the tepals as just before the nursery closed. These were raised well as the upperside. Bowles (1955) stated the by JJ Kerbert, a hybridizer for Zocher & Co. The Van Meeuwen lithograph came closest to the sales advert mentions: ‘Colchicum seedlings. plant’s appearance in life, so the outer stripe Beautiful large flowered hybrids of C. giganteum, should probably be ignored. C. speciosum and others × C. sibthorpii. Many retain Descriptions of ‘Violet Queen’ the beautiful pattern of the latter and they are The oldest catalogue description I have found (Van much stronger. There’s also a large fl, double Meeuwen 1937) does not offer much, giving ‘Violet flowered lilac pink, a hybrid with C. aut. fl. albo pleno’. Queen’ as ‘lilac, tinted violet’. Foerster (1939) describes ‘Violet Queen’ as ‘dark violet, big After further research, Johan found a reference Colchicum with an extraordinary intense colour… with a big white throat, a robust and floriferous form’. Bowles describes ‘Violet Queen’ as having ‘long pointed segments closely tessellated on a bluish lilac ground contrasting pleasantly with the 32 The Plant Review

Classification corner PUBLIC DOMAIN PUBLIC DOMAIN The lithograph by Esther Bartning (far left) shows ‘Violet Queen’ (second from top on the left) with a white stripe on the underside of the tepals. The Van Meeuwen lithograph (left, showing ‘Violet Queen’ middle, left) was identified by Bowles as the most accurate. conspicuously white throat and central channels of received as part of an old Czech collection. the segments’. Synge (1961) offers ‘Deep purplish Candidates 2 and 3 are German and considered violet with pointed petals and conspicuous white good contenders by Colchicum specialist Hagen throat, moderately tessellated. Mid-September’. Engelmann. Candidate 3 was once sold in the GDR The description in the Checklist in Grey-Wilson as Colchium × agrippinum. In the coming years it is et al. (2020) was based on an impostor in the 2014 hoped to grow these plants together with the aim trial so may be discounted. of deciding which, if any, are the true queen. Other lost cultivars Judging from the plates of Bartning and Van Other noble colchicums have also been lost to Meeuwen along with the descriptions by Bowles time: ‘Danton’ (perhaps still sold in Germany), and Foerster we can accept the following: ‘Violet ‘Ferndown Beauty’, ‘Glorie van Holland’, ‘Guizot’, Queen’ is a C. speciosum × C. bivonae hybrid of ‘Hidegkut’, ‘James Pringle’, ‘Klondike’, ‘Naeisanum’, average size with long, pointed segments and a ‘Petrovac’, ‘President Coolidge’, ‘Purity’, ‘Ruby dark colour. Along with ‘Conquest’ and ‘Danton’, Queen’, ‘Surprise’ and ‘W. Kerbert’. Perhaps they too ‘Violet Queen’ is the only cultivar Foerster describes might be found lurking in forgotten collections. as dark and the plates show a flower much darker than ‘Lilac Wonder’ or ‘Waterlily’, for instance. Wim Boens is a Belgian horticulturist with a particular The conspicuous white throat is not visible on interest in Ranunculaceae, Iridaceae and Araceae. either of the lithographs, it seems just to have Acknowledgements I am greatly indebted to Leonid a white star in its heart. Bondarenko, Hagen Engelmann, Christian Kreß, Rod Pretenders to the throne Leeds, Mariette Timmerman and Johan van Scheepen Two colchicums masquerading as ‘Violet Queen’ for their assistance with this article. have been detected. The most common of these in References Bowles, EA (1955) A Handbook of Crocus the Netherlands is now called Colchicum ‘Pride of & Colchicum. The Garden Book Club, London. Foerster, Holland’ and differs in being smaller, having pale K (1938) Edelherbstzeitlosen. Gartenschönheit 1938. pinkish purple, non-tessellated flowers. The other, Foerster, K (1939) Das Blumenzwiebelbuch. Verlag now named ‘Fellbrigg Violet’, is mostly found in der Gartenschönheit, Berlin. Grey-Wilson, C, Leeds, British private collections and its tepals are R & Rolfe, R (2020) Colchicum, The Complete Guide. uniformly coloured and only very lightly tessellated. RHS, London. Synge, P (1961) Collins Guide to Bulbs. Which is the one true queen? Collins, London. Van Meeuwen, GC (1937) G.C. van At present three clones are in the running. Meeuwen & Sons N.V., bulbgrowers & exporters: Candidate 1 is sold by Lithuanian nurseryman miscellaneous bulbs our specialty. 1937. Leonid Bondarenko as ‘Violet Queen’ which he 33 Digital taster edition

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