Aldrovanda is a genus of aquatic carnivorous plants with one known extant species, A. vesiculosa, the waterwheel plant. These plants can be found in warm, standing water in Asia, Africa, Australia, and Europe. They are also cultivated by hobby gardeners interested in aquatic plants or carnivorous plants, and are sometimes available from aquarium suppliers, as well as carnivorous plant catalogs.
The only known species of Aldrovanda produces whorls of leaves known for growing around the main stem like the spoke of a wheel. A single plant can produce numerous whorls, each supported with air bladders to keep the plant floating in the water. At the end of each spoke-like structure, a pair of leaves is positioned to form a trap similar to that produced by the famous Venus fly trap on land.
When aquatic organisms drift between the leaves, they brush against trigger hairs and the traps snap shut. Aldrovanda moves extremely rapidly and is the only aquatic plant known to trap prey in this fashion. Like other carnivorous plants, Aldrovanda has adapted to produce enzymes used to break down its prey for digestion. By free floating in the water, these plants have access to a continuous supply of nutrients.
These carnivorous plants flower rarely. When they do, they produce small white flowers buoyed up above water level with the use of air bubbles. After several hours above water, the flowers close and sink below the surface, allowing the plant to produce seeds. Aldrovanda can also reproduce by budding, and this reproductive method appears to be more common.
Although these plants are adapted to warm waters, they can tolerate cold winters. They do so by producing small and very tight leaf clusters designed to break off and sink to the bottom. The cluster buries itself in the mud to overwinter while the lighter leaves are allowed to float. The lighter leaves may be eaten by animals or can die off during the cold weather. When the weather warms up, the buried bunches of leaves emerge, leaf out, and start producing whorls. This adaptive technique has allowed Aldrovanda to survive even in climates where the weather grows hostile during the winter months.
Gardeners interested in cultivating A. vesiculosa may be able to obtain specimens from other gardeners. The plants can be grown in an aquarium or a pool in a carnivorous plant garden that may include other species like plants in the genus Drosera, the sundews.