Carnivorous Plants

Carnivorous plants are distinguished from other flowering plants because of their ability to trap and kill prey, digest the prey, and utilize the nutrients from the captured insect. Prey is lured to the plant by specialized leaves or traps, which may function as active or passive, depending on whether movement is involved in the capture.

These specialized plants are adapted to grow in lean, often acidic soil where nutrient levels are low. Carnivorous plants do photosynthesize but derive most of their nutrients from trapping and consuming insects.

While carnivorous plants seem exotic, some are native to the United States. Pitcher plants (Sarracenia) have passive pitfall traps, and many species will survive Pennsylvania winters. Pitcher plants have specialized tubular leaves that are often topped with a hood. The plant's nectar and brightly colored traps attract prey to the plant. The lip of the tube is slippery, and when insects land on the edge of the tube, they fall into the narrowing trap. Downward-pointing hairs on the inside trap wall prevent the insects from escaping. The prey is digested by enzymes, and the nutrients are absorbed by the plant.

The most popular carnivorous plant is the Venus fly trap (Dionaea muscipula). This active trap consists of two clamshell-like leaves that are edged with thick guard hairs. Normally, the leaves are held in an open position, but when triggered, the leaves quickly close, capturing the insect. The leaves close when the tiny trigger hairs on the interior surface of the leaves are touched twice. Once the trap closes, it seals and flattens. The struggling movements of prey cause the release of acids which begin to digest the prey. Digestion takes three to five days, and then the trap reopens.

Carnivorous plants with semi-active traps include the sundews (Drosera) and butterworts (Pinguicula). Sundews grow close to the ground and are easily recognized by the flat, red and green leaves that glisten in the sunlight. Stalked glands resembling tentacles cover the upper leaf surfaces and are tipped with tiny drops of mucilage. Prey is attracted to the leaves and quickly becomes stuck. Once captured, the leaf margins of the sundew may wrap over the prey.

Butterworts grow in a rosette and have bulbous yellow-green leaves. Plants are inconspicuous, except when in flower. Similar to sundews, butterworts trap prey on the mucilage-covered leaves. After the prey is trapped, the leaf margins slowly roll over the insect, and digestion begins.

Many varieties of pitcher plants can be grown outdoors if planted in the proper conditions. The northern pitcher plant (Sarracenia purpurea) will thrive when planted in full sun at the edge of a water garden. Pitcher plants and sundews can also successfully be grown outdoors in containers in hardiness zones 5 and 6. Select a container without drainage holes and fill it with a specially prepared soil media with low fertility, suitable for carnivorous plants.

Prepare the media by soaking and rinsing the following ingredients in distilled water or rainwater.

• 1 part – a combination of peat moss and long-fibered peat (be sure no fertilizer is added to the peat)
• 1 part silica sand or chicken grit

Fill the container with the medium and add the carnivorous plants. Place the containers in full sun and water regularly with distilled water when rain is not consistent. Containers will need to be overwintered in an unheated garage, cold frame, or protected outdoor site.

Carnivorous plants are not only fun and educational but also beautiful plants with intricate patterning and vibrant colors and are sure to spark conversation in the garden.