This meat-eater is aquatic
One of my students brought this one in the other day. It is a little plant worth a considerable amount of discussion. Here are a few thoughts.
This is a carnivorous plant, meaning that it is able to capture and digest animal life as a means of augmenting whatever minerals (especially nitrogen and phosphorus) are available to it in the wild. The animals used by carnivorous plants are generally quite tiny; no need to worry about falling into a carnivorous plant around here or anywhere else. The carnivorous Venus' fly-trap, which does grow our coast, is capable of capturing animals as large as small frogs. (Plant carnivory has always fascinated humans…you might want to see "Little Shop of Horrors" sometime.) You might be interested in knowing that the southeastern USA is one of the world's hot-spots for carnivorous plants. Our Mystery plant and Venus' fly-trap (Dionaea), represent two of the genera of them. The others are the sundews (Drosera), the butterworts (Pinguicula), and of course, the fabulous pitcher plants (Sarracenia). Are any of these represented in your area?
Our yellow-flowered meat-eater belongs to a genus of about 100 species found throughout the world. This one is an aquatic, annual species which develops a prominent floating device. This flotation structure consists of a number of branching “arms” that inflated with air, and which, as it develops, rises through the water of a quiet pond or ditch, ultimately bringing the flowering stem to the top. The underwater "floats" bear tiny traps on their edges. These traps are nearly microscopic, but highly effective in pulling in small aquatic critters that swim too close. A complicated mechanism, involving tiny trigger hairs and a trap door, is involved. Other, related species of our mystery plant don't float, but instead live on saturated or dripping soil. The flowers are clustered at the top of the aerial, leafless stem. Each flower has 5 bright yellow petals, and they are arranged in a very “bilateral” way. It's good to remember that the flowers don't “eat” anything…it is the tiny traps down under the water that do all that.
You might see our mystery plant in any of the coastal counties of the Southeast. It is fairly common, blooming now, and occurs from New Jersey south to Texas and Florida. Several brilliant yellow flowers –as bright as hot butter--occur near the top of the leafless stalk, and a pond full of thousands of these fascinating plants is a beautiful sight.
[Answer: "Floating bladderwort," Utricularia inflata
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 email@example.com.