Plant grows in well-drained soil

  • Friday, October 11, 2013

This is what we botanists call a "tuberous rhizome."

These fine lads are a couple of my students who have captured something strange! It reminds me of something from a monster movie: a cross between a potato and a scratchy, wiggly sea creature. But of course, it’s part of a plant…and it could be in your backyard!

This is what we botanists call a “tuberous rhizome.” Which means that it is an underground stem, more or less horizontal, and conspicuously swollen. (You will recall from Botany 101 examples of rhizomes and tubers: fresh ginger from the supermarket is a rhizome…an Irish potato is a tuber.) Its tissues are loaded with stored carbohydrates as well as a considerable amount of water, and if you were to cut into one of these things, it would have the consistency of a hard apple. In addition to providing a stored food source for the plant, it is very effective as a “perennating” organ, that is, allowing the plant to send up new stems repeatedly each spring. And of course, this means that if you have this plant growing in your yard and you don’t want it, you are going to have to do some pretty fierce digging.

This plant is a vine, one of over 300 related species found mostly in the tropics, and many of which may be very prickly. (Our mystery plant is not particularly thorny, however.) Its early stems are fleshy and succulent, and termed “leader shoots.”

They look something like giant asparagus stalks, and in fact, have been used as a food source. With age, the leader shoots become woody and hard, and sometimes form thickets. Tear-drop shaped leaves are produced on upper branches, and the leaves are shiny green on the upper surface. The vines are capable of climbing high into trees, by means of tendrils produced at the leaf bases, and then branching, forming thick dangling festoons of dark greenery. The vines are therefore quite handsome, conspicuous during the winter…and in the past, have sometimes been used as a Christmas decoration.

Flowers are produced in the summer, and these are small and rather drab, with six pale yellow perianth parts. A dozen or so flowers arise from the end of a short stalk, and thus form clusters. Each flower produces a single berry, these usually black when mature. The berries take about a year to ripen, and they are eaten by a variety of wildlife species.

You can see this plant rather commonly in a variety of natural habitats, usually on well-drained soils, rather than in swamps. It is mostly a coastal plain species, occurring from Delaware south to central Florida and then west to eastern Texas.

(Should you be so inclined to dig up one of these things, consider eating it--as your reward. It turns out that early settlers used these for food, fashioning a sort of mush out of them. I’m thinking that with enough butter, salt and a sprinkle of hot sauce, it’s probably delicious.)

Answer: “Jackson-vine,” “Catbrier,” Smilax smallii

John Nelson is the curator of the A. C. Moore Herbarium at the University of South Carolina, in the Department of Biological Sciences, Columbia SC 29208. As a public service, the Herbarium offers free plant identifications. For more information, visit www.herbarium.org or call 803-777-8196, or email nelson@sc.edu.

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