(Editor's Note: This article was originally published on October 31, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
The Corpse Plant, or Ghost Plant* (Monotropa uniflora) takes its name from its ghostly pallor. Except for the roots, all parts of this plant are a bloodless white, as if it had been drained by a vampire. It is also sometimes called Indian Pipe, from the shape of its flowers, but this name is not in keeping with our seasonal Halloween theme, so I will not use it here. "Corpse Plant" sounds properly ghastly.
Seeing the Corpse Plant in flower on a dark forest floor, you might suppose from its pallid coloring that it is some kind of fungus, and it is often mistaken for one. In fact, it is a herbaceous perennial that has been classified as part of the Ericaceae family, which includes rhododendrons, blueberries and cranberries. But unlike most members of this plant family, and like a fungus, the monotropes do not produce chlorophyll. It is the absence of chlorophyll that accounts for the ghostly white color of the Corpse Plant. Because it is incapable of photosynthesis, it must obtain its nourishment by parasitic means. Such parasitic plants are known as heterotrophic (Photosynthetic plants, producing their own nutrients from sunlight, are called autotrophic).
Even more unusual than a more typical parasite, the Corpse Plant, like other monotropes, does not directly parasitize the trees under which it grows, but rather feeds from the mycorrhizal fungi associated with the trees' roots. Unknown and unseen by most people, this class of fungus is vital to the growth of most plants in the world. The relationship is symbiotic, mutually beneficial. The fungus receives nourishment that the host plant produces by photosynthesis, and in return it helps the host take up vital nutrients and moisture from the soil.
The monotropes, including the Corpse Plant, attach themselves to the underground filaments (hyphae) of the fungus. There they leech away part of the nutrients that the fungus absorbs from the host plant. They are thus indirectly parasitic on the host and benefit from its photosynthesis, and directly parasitic on the fungus. Because of this they are called mycoparasites, or myco-heterotrophic ("myco" refers to fungus).
While the Corpse Plant has a wide area of distribution, primarily east of the arid Great Plains in North America, it is fairly rare. It is found most often in the dark undergrowth of woods, where it depends on certain specific fungi that colonize the roots of the trees that serve as its ultimate host.
It is a small plant, no more than a few inches high; its leaves, with no photosynthesis to perform, are reduced to small scale-like growths along the stems. As its scientific name suggests, the Corpse Plant produces a single flower, with no more than eight petals, on each down-curving stem. Some specimens may be pink or red in color.
Because of its very specific growth requirements and the complex relationship among the trees, fungi and parasite, the Corpse Plant is not suitable for transplanting and is difficult to propagate. Most people will have to admire it in the wild, if they can find it.
There is only one other species of monotrope, Monotropa hypopithys, also known as Indian Pipe and also as Pinesap. It primarily differs from M uniflora by producing a spray of several flowers on its stalk and having more coloration. It may be even more rare.
It would be fitting for a plant named the Corpse Plant to flower in late fall for the Halloween season, but in fact it is usually in bloom a couple months earlier. We can't have everything.
* Monotropa uniflora should not be confused with any other plant called "Ghost Plant," in particular Graptopetalum paraguayense —also known as Mother of Pearl Plant.