Biology Department

Pond Wall

These habitats range along a gradient from permanently flooded to periodically saturated soil and support hydrophytic (water-loving) vegetation at some time during the growing season. Our greenhouse has plants from ponds, marshes, and bogs. One of the most unusual types of hydrophytic plants are carnivorous plants.

Carnivorous plants are usually in bogs where the nutrient content of the substrate is low, and water and sunlight are abundant. Carnivorous plants can obtain nitrogen and phosphorus by digesting the proteins in the animals they capture.


A surprisingly large number of plants are able to catch and digest insects by means of specialized leaves. They include the Venus fly trap (Dionaea muscipula), sundews (Drosera), pitcher plants (Sarracenia, Nepenthes), butterworts (Pinguicula), and bladderworts (Utricularia). This carnivorous habit has arisen in six families, fifteen genera, and approximately 500 species, and always in plants specializing on nutrient-deficient environments. Thus, the carnivorous habit is a means of securing those nutrients that are in limited supply and not a means of securing energy since all of these plants are photosynthetic.

Venus fly trap (Dionaea muscipula). Insects crawling on the leaf surface contact trigger hairs (easily seen with naked eye) which initiate the closing of the leaf. Enzymes are secreted by surface cells of the leaf, digesting the insects. Please do not attempt to trigger the leaves. They probably won't react (too old, or too tired due to visitor abuse). These plants are native to the Carolinas.

Sundews (Drosera spp.) These plants are common in the bogs of Pennsylvania. Notice that the leaf blades are covered with long sticky hairs. Insects get stuck and in their struggle, trigger the hairs which then bend toward the leaf surface where the insects are finally digested.

Pitcher plants (Sarracenia spp., Darlingtonia californica). The pitchers (modified leaves) have stiff rims with nectaries to attract insects. Many insects fall into the pitcher and cannot crawl out because of the stiff downward-pointing hair zone and the waxed, slick regions on the pitcher walls. Sarracenia bogs are common throughout the East while Darlingtonia bogs occur in Oregon and California.

Tropical pitcher plants (Nepenthes spp.). These are beautiful epiphytes in which the leaf midrib is prolonged into a tendril which bears a pitcher at its tip. These pitchers are not designed for water storage, If they were meant to trap rain water, why put a lid on them? In fact, they are for insect-trapping. It is very rare for epiphytes to also be carnivorous. Despite the presence of digestive enzymes in the pitchers, there are certain species of algae and even insect larvae which live a happy coexistence with the plant while immersed in the fluid. How they withstand the enzymes which digest other creatures is uncertain.

Butterworts (Pinguiculaspp.). The leaves of these species ensnare prey with a sticky glandular secretion. Once caught, an insect is enrolled by the leaf margins and digested or, in some species, is covered by digestive fluids that fill a dish-like depression that forms around the prey.

Bladderworts (Utricularia spp.). Highly sophisticated bladder traps of these species open with extreme rapidity to catch tiny prey. Borne underwater, in wet sand, mud, or moss, or in bromeliad tanks, prey are pushed into the bladders by water sucked into the vacuum created within the bladder.