Burmese grape

Back in June 2006 I saw a wonderful tree of Burmese grape (Baccaurea ramiflora, Phyllanthaceae (Euphorbiaceae)) loaded with fruits. The Dokmai Garden seedling from that tree had a very rough childhood, suffering in the striking sun and its leaves were constantly eaten by insects. Today, it is taller than me and flowers for the first time!

This is the original mother tree photographed north of Chiang Mai in June 2006. The fruits may resemble those of longkong/lansat/duku of the mahogany family (Lansium domesticum, Meliaceae), but the Burmese grape has a more reddish tinge of both peel and pulp. Both fruits can be confused with longan fruit (Dimocarpus longan, Sapindaceae) of the litchi family, but longan pulp is one unit while Burmese grape and longkong have segments. The scientific name Baccaurea is derived from Latin ‘bacca’ meaning ‘fruit’ and ‘aureus’ meaning ‘golden’. The Central Thai name is ‘mafai’.

The first flowers of the Dokmai Garden seedling, February 2nd, 2013. The scientific name ‘ramiflora’ means ‘flowers grown on branches’. The flowers seen in this picture are male, and most literature claim Burmese grape is dioecious, i.e. you would need a female plant individual to get the fruits. However, I have several times seen solitary trees far from any other tree individual, loaded with fruits. Where do these female trees get the pollen for fertilization? I spoke to Ketsanee’s parents who said that one tree is enough, contradicting the theoretical literature. Some literature also claims that female flowers are mainly born on the older branches and trunk, and male flowers mainly under the leaves. This individual has a bounty of flowering buds also far down on the main trunk and I am therefore most curious to see them when they open.

Other species of Euphorbiaceae may have plant individuals forming male and female flowers at different times, such as Jatropha podagrica, but according to my observations they may overlap for a short time. In the closely related tropical cranberry (Antidesma bunius, Phyllanthaceae) which we also grow here at Dokmai Garden, the male and female trees are indeed separated. The sexes still meet thanks to the terrible stench of the flowers, attracting carrion flies which perform the pollination. I can not detect any fragrance of the Burmese grape flowers.

The reason to separate male and female blossom, either in time or between individuals, is to promote cross-pollination, resulting in seeds with a higher genetic diversity to ensure survival in an everchanging world. In animals that is OK because males and females can seek up and find each other, but plants can not move. A lonely tree boy would be very lonely. The separation of boy and girl plants are rare in the plant kingdom (less than 10% of the plant species), and to my knowledge that would mostly occur in species forming natural monocultures, such as date, willow or governor’s plum. Burmese grape does not fit that profile so something fishy is going on. However, there are other mechanisms to prevent self-fertilization, so the actual number of plant species adapted to prevent that is greater.

Dicliny is a phenomenon where each flower is unisexual (either male or female, not androgynous like in the majority of plants). Coconut has dicliny but the two flower genders occur in the same inflorescence. A dioecious plant species has different male and female plants, like in date palms. Some plants like papaya may produce seeds which are either female, male or androgynous. Since Burmese grape is not a big commercial crop, and since old back-yard trees die with the older Thai generation, knowledge about it is scarce. Are the conflicting observations due to a mix-up of species, a mix-up of dioecious and monoecious cultivars like in papaya, the ability to form male and female flowers at different times or different sites in the same tree or unawareness of nearby males? I urge the Dokmai Dogma readers to share information from actual cultivation of the Burmese grape! We have to trust our eyes here, not sayings.

Another interesting question about its biology is what insects pollinate it? The male flowers are tiny, 2 mm, and the sepals are curved over the stamens, so I do not believe wind is a pollinator. When I studied the flowers under the microscope I saw thrips, and according to Haegens (Flora Malesiana) thrips as pollinators are a theoretical possibility. In the old world tropics, bees, beetles and flies are the most important pollinators. Again, please share if you know or if you have made observations!

Although Flora Malesiana claims Burmese grape is a species from primary rain forests, a statement repeated by Flora of Thailand, that can not be its restriction since it also grows in monsoon areas such as northern Thailand, Burma, Vietnam and Assam. However, judging from my own cultivation efforts and ‘A Field Guide to Forest Trees of Northern Thailand‘ it seems to demand evergreen forests. The Dokmai Garden seedling was planted in 2007 and did not take off until two years ago when it got sufficient shade from the adjacent evergreen Artabotrys hexapetalus (Annonaceae).

Although the fruits are frequently sold in the local markets, it is not commonly planted in the Chiang Mai valley so a sight is a delight. I believe the rare occurrence is due to its need for care (moisture and screen), while most local home gardeners are used to fruit treesthey can grow without effort (e.g. mango, longan, banana, strawberry tree, guava, Indian jujube, tamarind, coconut, hog plum, papaya and pineapple).

The genus Baccaurea encompass many species in the Indomalayan and western Pacific regions, but very few species have been domesticated. In Flora of Thailand (8:1) Dr Kongkanda lists 12 species growing in Thailand. Baccaurea racemosa is another commercial species you may encounter further south in the markets of Malaysia and Indonesia.

Baccaurea ramiflora was coined by the Portuguese jesuit Joao de Loureiro in his Flora Cochinchinensis from 1790.

Text & Photo: Eric Danell