Dioscorea (2013)

By Eric Driskill (October 2013)

The genus Dioscorea is in the family Dioscoreaceae and includes over 600 species. The plants are native throughout tropical and warm, temperate locations. They range from Africa to Mexico and South America.

The name honors the Greek botanist Dioscorides. Several species are yams, which are an important food crop in many tropical regions. Some of the yams need to be detoxified before eating. The toxin steroidal saponins, found in many species, is made into steroid hormones used in medicines.

The plants are tuberous, herbaceous perennials. There are at least 19 species. They form a caudex and are of particular interest to succulent collectors.

The vining caudiciform species found in most succulent collections are the above-ground species. The plants have typically heart-shaped leaves arranged in a spiral. The small flowers are greenish-yellow. Most Dioscorea species are dioecious, with separate male and female plants, though a few species are monoecious.

The size and color of the flowers are certainly not the main attractions for these plants. A nicely grown plant with a mature caudex, however, is a true sight to behold. The caudices of some of the nicer species are covered with thick, corky plates. Certainly some plants have deeper plates than others, but in my experience, a plant grown slowly and hard has nicer plates than those grown faster.

One of the more popular species is D. elephantipes, also known as elephant’s foot or Hottentot bread. The name elephant’s foot is due to the shape, size and texture of the caudex, which resembles the foot of an elephant. “Hottentot bread” is due to the plant’s high concentration of starch.

D. elephantipes earned the Royal Horticultural Society’s Award of Garden Merit. The plants can reach over 10 feet in circumference and over 3 feet tall. Don’t worry about calculating the square footage you may need for a plant that size any time soon, though.

The plants are propagated by seed, and don’t grow particularly fast. Most available plants are seedlings the size of a golf ball, but you can find larger plants for much more money. It is hard to find a larger specimen with plates that haven’t been damaged, though.

I think part of the appeal of dioscoreas is to buy them young and grow them, witnessing the bark splitting into various geometric shapes. The grooves between the plates grow deeper and deeper. In just a few years, you will have a plant that may have what it takes for the next victim of our hobby to fall prey to the allure of these wonderful plants.

These plants certainly don’t read succulent literature to know when to grow. Some grow in winter, some in summer, and others when they see fit. The plants enjoy shading for their caudices with their leaves in the sun, but they do not tolerate frost. In cultivation in temperate areas, D. elephantipes requires the protection of a heated greenhouse.