There are about 80 species in the genus Dischidia, which is a member of the Asclepiadaceae, or milkweed, family. Most of the species are myrmecophilous, or ant-loving plants, which provide living quarters for the ants. Dischidia plants are trailing, or scandent, climbing plants that usually live on trees in parts of Australia, western Asia, and western Pacific areas. Growers generally grow them in hanging pots, in pots with trellises or climbing materials, and similar situations. People typically raise them for their unusual foliage, which is dimorphic, meaning the leaves grow in more than one shape or form.
In the wild, Dischidia plants and the ant species philidris have a symbiotic relationship in which the plants offer the ants living space and the ants reciprocate by feeding the plant. Some of the leaves on the plants are hollow, and the ants use these "rooms" as nurseries. The plants obtain nitrogen and carbon from the ant debris, such as ant excrement, dead ants, and uneaten parts of insects. The plants absorb the carbon dioxide that the ants exhale, and this exchange helps the plant retain water. Some species have leaves that lie flat to a tree trunk and provide shelter for the ant colony.
It is these unusual leaves that growers generally find fascinating. The inflated ant chamber leaves account for some of the common names. D. pectinoides, called kangaroo pocket and thruppence ravioli plant, has pouch-shaped leaves that are flatter and more elliptical than most other species. Other species have leaves that may be rounded, balloon-like, or pickle-shaped. Thruppence urn plant does not have inflated leaves, but has large, flat leaves that the ants live under as it clings to tree trunks.
The waxy Dischidia flowers are not large and showy. Generally, they are small, pitcher-shaped flowers that often are borne at the axil where a pair of leaves grow. Many appear at alternate leaf pairs. Flower color ranges from white to red, and most have five petals at the top of the swollen pitcher-shaped base.
The button orchid, or D. nummularia, also goes by the name watermelon Dischidia because the leaves resemble watermelon rind in colors and markings. The variegated leaves may have some rosy tint, especially when exposed to sunlight. Generally, growers raise it as a hanging plant or as a climber. Another attractive climber is the D. rafflesiana, or Malayan urn plant, which has yellow-green leaves that may be up to 1 inch (about 2.5 cm) long. It grows elongated, narrow ant chambers randomly along the vine among its round, flat leaves.
Growers propagate the Dischidia plants with stem cuttings or by sowing the seeds. Generally, they are not a garden plant and grow in pots of some sort. They prefer temperatures above 60°F (about 16°C); dry, soil-less root substance; and moderate to high humidity. In the wild, the ants help the plant to conserve water, but in cultivation the plants need more humidity.