In a previous article I introduced you to a parasitic jungle plant called Rafflesia, the world's largest single flower. Here I'll introduce you to a group of parasitic desert plants that are even more bizarre. One species actually flowers underground! Read on to learn more about these enigmatic plants . . .
Stranger and Stranger
Just when I think I've seen the strangest of the strange, I find another amazing plant that trumps my previous winner. Hydnora africana, a parasitic plant in the family Hydnoraceae, has no leaves and is generally seen only when in bloom. This characteristic may seem to be similar to the way Rafflesia grows, but Hydnora differs in that it has an underground structure from which the flowers arise. One could argue as to whether this underground structure constitutes "roots", a modified stem, or something in between. Whatever this structure is, the bloom buds arise from it. This structure also has protuberances which can attach to host roots for sustenance.
Each species has different hosts; Hydnora africana has been seen on soil near the base of Euphorbia mauritanica and Euphorbia gregaria, two succulent Euphorbs in Namibia. The unusual tripartite blooms of H. africana (see thumbnail above, right) emerge completely above ground. Another species, Hydnora triceps, is one that blooms underground (see photo of two unearthed blooms at left). H. triceps uses Euphorbia dregeana exclusively as host. The emerging bloom bud pushes up the soil so that a crack forms in the soil surface. This crack allows pollinators access to the bloom underground. How do the pollinators know there is a bloom there? Well, these flowers have a fetid odor which serves to lure the unsuspecting insects in to do the pollination work. In most Hydnora species, the female portion of the bloom is receptive first, then the next day the male portion releases pollen.
Getting to the Root of the Matter
One aspect of these plants that I found particularly interesting is the underground parts (see photo to right). I hesitate to describe them as "roots" because they look much more like specialized underground stems. Actually, they bear a resemblance to a strange type of tentacle and do remind me a bit of some fictional underground horror movie creatures I've seen! These structures seem to be able to store water and nutrients because they are succulent in cross section. I imagine they are a horror to the plants being parasitized, though.
Hydnora blooms generally do have both male and female parts, but the pistillate portion is receptive the first day, and the next day the staminate portion releases pollen. Other changes happen in the flowers, too, as the maturation process proceeds. Pollinators may include beetles, ants and flies. Some species produce fruits that are actually palatable to people!
While Hydnora is an Old World genus, found in Africa, a genus of the Hydnoraceae does exist in the New World, and that genus is Prosopanche. These plants show similarities to Hydnora in morphology and bloom structure. However, they have completely different hosts, and are native to Argentina. For example, Prosopanche americana has Prosopis, a member of the Fabaceae, or legume family, as host. The blooms on Prosopanche blend in much more with earth tones, not having any light or brighter colors as some of the Hydnora species do.
LariAnn has been gardening and working with plants since her teenage years growing up in Maryland. Her intense interest in plants led her to college at the University of Florida, where she obtained her Bachelor's degree in Botany and Master of Agriculture in Plant Physiology. In the late 1970s she began hybridizing Alocasias, and that work has expanded to Philodendrons, Anthuriums, and Caladiums as well. She lives in south Florida with her partner and son and is research director at Aroidia Research, her privately funded organization devoted to the study and breeding of new, hardier, and more interesting aroid plants.