Dionaea is a genus of carnivorous plants with only one known species, D. muscipula, the Venus fly trap. This is an example of a monotypic genus, a genus with only one species. The origins of the Venus fly trap are not well understood, but it occurs natively in only region, North and South Carolina in the United States. It has been successfully introduced in other areas of the world, but is a cause for conservation concern in its native habitat.
This carnivorous plant produces a basal rosette of long, broad leaves. Each leaf is terminated with a two-lobed trap. When relaxed and open, trigger hairs on the inside of the trap are exposed. If two hairs are touched in succession, the trap snaps shut, and the mesh-like structure at the sides of the trap keeps the prey trapped inside. Then, the plant can begin digesting its meal. If the prey writhes in the trap, it will trigger the Dioneae to digest more rapidly.
A number of safeguards have been developed by Dionaea to avoid inefficiency. Opening and shutting the trap requires energy, and the plant wants to avoid snapping shut in response to a false alarm like a drop of rain. Requiring two or more trigger hairs to be touched makes it more likely that the plant will snap shut on something alive. In addition, the mesh at the edge of the trap allows small prey to escape, allowing the plant to focus on large prey with lots of nutritious value.
This plant grows very slowly. Dionaea can propagate from seeds, with seedlings taking several years to mature. The rosettes of leaves can also divide, usually underground, and produce more plants. Venus fly traps are native to swamp environments and require a very humid climate and wet sandy or peaty soil. Many people who cultivate these plants use partially closed containers to keep humidity high.
In the spring, a healthy Dionaea will put out a single stalk topped with white flowers. Gardeners often pinch the stalk back to encourage the leaves to develop. Because the plant grows slowly, helping the plant conserve energy by shutting down flower production can be beneficial.
While Dionaea has a reputation for being hard to grow, it is actually relatively easy to cultivate. It can be grown indoors or outdoors, and tolerates being fully submerged in water as well as being subjected to relatively cold weather. To meet the plant's nutrition needs indoors, people should make sure to trap insects and feed the plant periodically. Meat is not an appropriate food for Venus fly traps, but people having trouble locating insects can use small meal worms from a pet supply store.