Plant 113

Phyllanthus montanus (Sw.) Sw. (Phyllanthaceae)


Phyllanthus montanus is a curious, large shrub endemic to Jamaica where it occurs in woodland and thickets. Although locally common, Phyllanthus montanus is listed as rare and near-threatened on the IUCN Red List of Threatened Species because of its restricted global distribution.

Superficially, Phyllanthus montanus appears to have compound leaves but closer examination shows that the dark-green, glossy, leaf-like structures cannot be true leaves. This species has cladodes. Evolutionarily, the leaf-like structures are flattened stems, performing the same photosynthetic function as leaves. Tiny flowers are borne along the stem margins. True leaves are reduced to tiny, non-photosynthetic scales associated with the flowers. The position of the flower gives rise to the genus name Phyllanthus, from the Greek phyllon (leaf) and anthos (flower).

The pale-yellow, translucent flowers are produced in profusion, their fragrance reminiscent of chip-frying oil. Moths are the species' most probable pollinators. The female moth lays her eggs in the flowers and simultaneously carries out pollination. This ensures there are fruits in which her larvae can develop and provides them with their first meal.

The genus Phyllanthus was once part of the family Euphorbiaceae but the genus produces a clear, non-phototoxic sap unlike many members of the Euphorbiaceae. There are more than 800 species of Phyllanthus making it one of the largest genera of flowering plants. Species can be found in tropical and warm temperate regions of Asia, Africa, Central and South America.

Many uses have been found for members of the genus Phyllanthus. Extracts of the pan-tropical weed Phyllanthus amarus have been shown to reduce or eliminate detectable hepatitis B virus (HBV) surface antigen in humans. Found in the blood, these HBV surface proteins are one of the earliest signs of HBV infection. Leaf extracts of Phyllanthus piscatorum are an effective poison used in hunting fish in Venezuela. This species is also used in the treatment of fungal infections in humans and as a substitute for tobacco. Other members of this genus are used in basket making, provide dyes and edible fruit. Many species are used locally as medicines.

The stems of Phyllanthus montanus give the shrub the appearance of an evergreen. It adapts well to cultivation but needs a minimum temperature of 15 degrees Celsius, hence its place in the Oxford Botanic Garden glasshouses. Phyllanthus montanus grows well in most soils as long as it is fed regularly, preferring a position in full sun or partial shade.

Further reading

Gertsch J et al. 2004 Phyllanthus piscatorum, ethnopharmacological studies on a women's medicinal plant of the Yanomami Amerindians. Journal of Ethnopharmacology 91: 181-188.

Huxley A 1992. Dictionary of gardening. The Royal Horticultural Society.

Kato M and Kawakita A 2009. Repeated independent evolution of obligate pollination mutualism in the Phyllantheae-Epicephala association. Proceedings of Royal Society B 276: 417-426.

Kate Pritchard