Carnivorous Plants Article by: Jessica Warren, ANR Agent in Camden County
Possibly my favorite thing about working in Extension is learning and sharing about the odd and fascinating things in nature. One of the topics that falls into that category is carnivorous plants. Carnivorous plants have adapted to nutrient poor soils in their native habitats by obtaining nutrients from insects. Carnivorous plants trap insects and digest them with enzymes and bacteria. The ability to utilize nutrients from insects in addition to photosynthesis makes carnivorous plants highly competitive in nutrient poor habitats such as various types of bogs and wetlands.Carnivorous plants are found throughout the United States, but occur in large numbers and diverse types in many of the floodplains and wetlands of the Southeast.
Carnivorous plants thrive in areas with little to no drainage and low levels of essential plant nutrients. These habitats usually have soils that are acidic and/or have a high clay content. This keeps nutrients in the soil from being available to plants for absorption.
Perhaps the most common types of carnivorous plants in Camden County are sundews. Most species of sundew grow low to the ground and capture both crawling and flying insects. The sundews I’ve seen locally are tiny, red and quite easy to miss. The red pigment absorbs ultraviolet light that attracts insects and acts as a visual lure for prey. Sundew leaves are covered with hairs that have sticky glands at the tips. The sticky substance reflects sunlight giving it the appearance of sparkling like dew (hence the name). The dew-like substance is a sticky mucus that contains digestive enzymes. When insects crawl across or land on the leaves they become trapped by the sticky mucus – and as they struggle – the leaves excrete more digestive enzymes and curl up to prevent the prey from escaping. Larger sundews can even trap and digest lizards and small rodents. Sundews produce small flowers, and the seeds they produce can remain viable for up to fifty years. Sundews are found throughout the US and Canada in moist, acidic, nutrient deficient soil. Sundews have been found to have a number of medicinal properties and uses.
Another common carnivorous resident of Camden is the butterwort. There are four species of butterwort in the Southeast, growing primarily in moist sandy soil or shallow water on the coastal plain. Butterworts have a rosette of yellowish-green leaves with a “buttery” feel. The leaves have tiny hairs on the upper surface that contain glands that excrete a sticky digestive substance. Small insects land on the leaves where they become trapped and digested. Butterworts are easy to overlook amongst grass and other groundcover species. The rosettes of leaves are small, and are easiest to spot when flowers are present. Our local butterworts usually produce white or purple delicate flowers.
Bladderworts are a fascinating group of aquatic carnivorous species. They are found in lakes, wetlands, ponds, and quiet coves of rivers and streams. Bladderworts do not have roots, and are usually found in waters that have a low pH and low nutrient levels. Bladderwort flowers bloom several inches above the water. They are shaped to attract pollinating insects and effectively remove pollen from them. Bladderwort flowers are attached to a leafless stem which is held above the water by submerged, inflated leaf stalks which radiate out from the main stem like spokes on a wheel. Floating below the submerged stalks are small leaves covered with bladders. Each bladder has a flap of tissue that is covered with trigger hairs. When small insects or crustaceans swim by and trigger the hairs, the flap opens causing a change in water pressure which forces the prey into the bladder where it becomes trapped and digested by bacteria and enzymes.
There are several species of pitcher plants throughout Georgia. Pitcher plants have tubular leaves with lids or hoods at the top that attract prey by secreting nectar. Once insects land on the lip of the pitcher, they slip on the waxy opening and fall into the tube of the plant. The pitcher plant has downward facing hairs in its tube which keep the prey from crawling back out. Insects drown in the fluid at the bottom of the pitcher or die of exhaustion and are digested and absorbed by the digestive enzymes that the plant secretes.Venus fly traps are perhaps the most popular carnivorous plant – and certainly the most famous. Though there are no native species in Georgia, they are still worth discussing.
Venus fly traps are native to select environments in North Carolina and South Carolina where they are protected by law and listed as an endangered species. Plants for sale in nurseries are grown from tissue culture, not harvested from the natural environment. Insects are attracted to the nectar glands in the Venus fly trap leaves. The leaves have thick claw-like hairs on the edges, and when an insect touches two hairs – or one hair twice – the leaf snaps shut, trapping the insect for digestion. The struggling insect stimulates the leaf to start secreting digestive enzymes. Interestingly, researchers have found that the trapping mechanism is only activated by insects. The plant won’t waste energy on other items touching the hairs!
Habitat loss and degradation are major threats to carnivorous plant conservation. Small isolated wetlands are the most valuable habitats for maintaining carnivorous plant biodiversity, but they are also the most at risk for development, pollution and land use changes. In addition, the loss of natural fires (and absence of control burns in their place) allows woody species that would naturally be kept in check by fire to outcompete carnivorous plants. Another threat for carnivorous plants and other unique wetland plant life is feral hogs. Feral hogs decimate our native wetlands and their plant life.