Plant of the Week, 29th January 2024 – Parietaria judaica (Pellitory of the Wall)

P. judaica on an ancient boundary wall, in open conditions on a sunny day, at Inchcolm Island, near Edinburgh. August 2023. Photo: John Grace.

This is a native species, well known to the herbalists of old, common in England but less common in Scotland. Here in Edinburgh we occasionally see it growing on walls next to pavements; in Glasgow and on the western side of Scotland it is hard to find. The most I’ve seen in one day was last summer when I visited the Inchcolm Island in the Firth of Forth, Scotland. The second most I’ve seen in one day is in Melbourne, Australia, where it is a frequent alien ‘weed’ of suburban streets, occupying much the same habitat as it does here in Britain. Its English name ‘Pellitory of the Wall’ distinguishes it from several plants in the daisy family that are also sometimes called ‘pellitory,’ and ‘of the Wall’ points to its favourite habitat. It thrives in the high pH mortar of walls.

P. judaica on the river wall at Musselburgh. Close up images show upper–female flowers above unopened male flowers, and lower-male flowers open and in bud. Images: Chris Jeffree, from his earlier blog on the Urticacae 6th July 2020.

It is a perennial plant belonging to the same family as Stinging Nettle, the Urticaceae. It does not sting, but its pollen is a serious cause of asthma, especially in Mediterranean countries where it is common. Its leaves are softly hairy. Its flowers are usually unisexual, in tight clusters, and it blooms for the whole summer, releasing pollen and causing Hay Fever (allergic rhinitis) with the familiar miseries of runny nose, itchy eyes, congestion and sneezing. It dies down in winter and overwinters with its tap root penetrating crevices in walls or rocks, and sprouts in the spring.

Detail of male flowers showing the pale anthers. Detailed drawings of the male and female floral parts can be found at the end of the taxonomic paper by Townsend (1968). This image: Chris Jeffree.

It is ironic that this species, sometimes called ‘the asthma plant’ was highly valued in herbal medicine from the earliest times (most notably, by Dioscorides, in his De materia medica, the precursor of subsequent herbals published over a period of two thousand years). Possibly, the reason for its abundance on Inchcolm Island is the presence on that island of an ancient abbey, founded in the 12^th century and said to be the most complete surviving remains of any Scottish monastic house. The monks and nuns in medieval times would have cultivated medicinal plants¹ and the species may have survived from those times (see also evidence from Ireland). In Plant Life in Edinburgh and the Lothians Smith et al (2000) give its habitat as ‘old walls, often those of castles, rocks’ and mentions the castles of Borthwick, Craigmillar, Roslin and the nearby Horthornden. Whilst these castles are not monastic they are all very old and their owners may have cultivated medicinal plants. It was used to cure a wide variety of ailments according to Gerard’s Herbal and Culpeper’s Complete Herbal, and a more recent text says it is much valued for its diuretic action and useful for dropsy and gravel² complaints (Allen and Hatfield 2004). Even today, a tincture of Pellitory of the Wall is available at Edinburgh’s best-known herbal dispensary and current research demonstrates wide biological activity of extracts from this species, although I have been unable to find any examples of clinical trials.

P. judaica on a suburban street in Melbourne, January 2024. Images: John Grace

Its first appearance in Australia was in New South Wales, around the year 1900; later it was recorded in New Zealand in 1946. Murray and Phillips (2012) point our that since European colonisation in the 1770s, as many as 26,242 alien plant species have been introduced to Australia. Of these, 130 are considered to be invasive (with deleterious effects on native biodiversity), and P. judaica is one of these. Most of the 130 were ‘deliberately introduced’ but P. judaica is listed as ‘accidentally introduced’.  The seeds are quite small (1–1.2 mm long and 0.6–0.9 mm wide) and rather sticky, thus the plant could easily have arrived on muddy boots or in shipments of almost any goods (we can never be sure). One Australian web site called weedfutures defines the species as a ‘noxious weed’ and suggests control using glyphosate. The names have been used in Australia: Asthma Weed, Dead Nettle, Kirribilli Curse, Pellitory, Pellitory-of-the-wall, Sticky Weed, Wall Pellitory.

It does seem to be much more troublesome as a weed in Australia than it is here. I found this quote on a popular gardening site:

“….Kirribilli Curse, sticky weed or asthma weed. It came to Australia on boats carrying marble from Italy hence Kirribilli Curse – where it was first found. Known to set off asthma attacks. Unfortunately it is glyphosate (RoundUp) resistant at the normal application rate of 10mls/l – you need to take it up to 30 – 40 mls/l. Hand weeding is difficult as it love to grow in cracks and crevices but the prongs on a daisy weeder will get to the roots. Otherwise, cook the damned weed with a Hot Devil weed-killing flamethrower…. This stuff brings my skin out in itchy red rashes. It’s evil and I cannot completely eradicate it”.

Kirribilli is a harbour-side suburb of Sydney in New South Wales, and the association with imports of marble seems credible, although I have been unable to find further reference to this rather intriguing link with an Italian source. The reference to skin rash also seems credible as shown here, but many other plants also cause skin irritation.

Another image from Inchcolm showing the plant growing in the crevice between stones on the boundary wall. This site is exposed to salt spray, and it seems the species does have some tolerance to salt. Image: John Grace.

The British distribution is predominantly southern, lowland and somewhat coastal, perhaps reflecting the pattern of calcium-rich sites or (possibly) long-ago cultivation. It may have been much more widely distributed in former times: Culpeper’s Complete Herbal of 1653 says “it grows wild generally through the land, about the borders of fields, and by the sides of walls, and among rubbish”. However, in recent decades the pattern has not changed very much. Globally, the species has found its way to the Americas, presumably the result of accidental dispersal by humans.

Distribution of P. judaica. On the left, Britain and Ireland. On the right, World and Australasia. Data from BSBI and GBIF.

There is a closely-related but much rarer species known as the Eastern Pellitory-of-the-wall, Parietaria officinalis, reported from Inverleith Park, Edinburgh, by Maria and David Chamberlain in 2020, and then by Sue Jury in 2022. It is taller and more robust, and there are differences in the flowers as illustrated by Townsend (1968).

The name Parietaria may be from the Latin word ‘paries’ (a wall) and judaica means ‘of the Jews’. The scientific name was coined by Linnaeus in 1763, but the plant is sometimes called Parietaria diffusa.

Notes

¹The most complete list of medicinal plants cultivated in medieval monasteries is surely the one from Westminster Abbey (Harvey 1992). Pellitory of the Wall is one of very many in Harvey’s list.

²dropsy is the old name for ‘oedema’ or ‘edema; dropsy is kidney stones.

References

Allen DE and Hatfield G (2004) Medicinal Plants in Folk Tradition. An ethnobotany of Britain and Ireland. Timber Press, Cambridge.

Harvey JH (1992) Westminster Abbey: the Infirmarer;s Garden. Garden History 20, 97-115. https://doi.org/10.2307/1587038

Murray BR, Phillips ML (2012) Temporal introduction patterns of invasive alien plant species to Australia. NeoBiota 13: 1–14. doi: 10.3897/neobiota.13.2422.

Townsend CC (1968). Parietaria officinalis and P. judaica.  Watsonia 6, 365-370.

©John Grace