Plant Families including Succulent Species

Dioscoreaceae - Wild Yams

The Dioscoreaceae is a group of 8 genera and over 600 species, including many caudiciforms or species with an underground tuberous root. A climbing vine with heart shaped or lobed leaves, and without tendrils, is produced from the tuber and may be a seasonal growth, or a more permanent one, depending on the species. The fruit is a berry, capsule or samara, and the seeds are usually winged and flat. In some species e.g. D. bulbifera aerial tubers are produced from leaf axils along the vine.

This family includes the edible yams which were cultivated in Africa and Asia around 10,000 years ago and are important crops in tropical countries. The African native Dioscorea rotunda is the most important cultivated species with over 200 cultivars. Many species of yam contain toxins and require careful preparation before they can be eaten safely.
The tubers of the wild yams Dioscorea villosa and Dioscorea mexicana contain steroid precursors from which the constituents of the old progesterone birth control pill were synthesised.

Dioscorea

The best known species in cultivation is the "Elephant's Foot" Dioscorea elephantipes (was Testudinaria elephantipes) (right) which produces a seasonal growth with very glossy heart shaped leaves and clusters of small yellow flowers in late summer from a distinctive caudex covered with greyish-brown corky bark that becomes deeply fissured into polygonal segments with age.

Dioscorea sylvatica produces a lobed caudex with smooth corky bark and a more or less permanent vining top growth, although leaves and stems die and are renewed throughout the year.

Testudinaria elephantipes

Tamus

In England and Europe, Tamus communis = Dioscorea communis (Black Bryony) is moderately common in hedgerows and woodland margins, forming a large underground tuber from which arises a seasonal twining vine with characteristic glossy heart shaped leaves, small greenish-yellow flowers and bright red glossy berries in the Autumn.

While the leaves are convincingly similar to those of the African "Elephant's Foot," the tuber can not be successfully grown on the surface for display. The plants are either male or female, so careful selection of cultivated plants is needed to obtain the attractive berries.

The tubers and berries are very poisonous, yet "Black Bryony" figured in traditional herbal medicine as a powerful diuretic. The result of an overdose was a painful death. External application of the mascerated tuber was safer and used to treat bruises, chillblains, gout and rheumatism.

Tamus communis

Note: the English "White Bryony" is a Cucurbit with different toxic and herbal properties. Both Black and White Bryony may be sometimes found growing together.