Usually, when we think of "carnivorous," animals come to mind. Yet there are some wonderfully fascinating plants that eat animals! It seems a contradiction, but this meat-eating habit of some plants is an interesting and normal adaptation of Nature. Carnivorous plants have evolved in places where the soil is poor and low in nutrients. Here, animals can provide the missing ingredients needed for survival. The carnivorous plants' fascinating methods of luring, trapping and digesting animals provide an adequate supply of necessary nutrients.
Carnivorous plants do not exist solely by eating insects. Like all green plants, they require sunlight for photosynthesis. As a matter of fact, they prefer the bright, open, sunny areas of Sphagnum bogs. It is in such places that an abundant and constant supply of water washes minerals from the area, leaving it nutrient-poor and often acidic. Most plants cannot grow well under these conditions. However, the carnivorous habit gives these plants a competitive advantage over other plants in the area.
When these plants were first discovered, the commonly observed prey was insects, hence the name "insectivorous plants." Many varieties have since been found including some which digest frogs, lizards, worms and other animals. Because of this, the term "carnivorous" meaning "meat-eater" is more general and is commonly used with these plants. Throughout this Website carnivorous plants will be referred to as "CPs." By the way, the only man-eating CPs are found in science fiction lore.
The part of the CP that attracts and captures prey, the trap, is actually a modified leaf. They come in many varieties and shapes and are generally divided into three groups: active, semi-active, and passive traps. Active traps, like the Venus Flytrap, show rapid movement when capturing prey. Semi-active traps, like the sundew, close very slowly over a period of hours. Sticky drops of "dew" keep their prey from escaping in the meantime. The passive traps, like those found in pitcher plants, are generally tube-shaped snares that lure prey into an inescapable pit.
After entrapment, the prey is digested and its nutrients are absorbed by the trap. From a chemical standpoint the digestive process is very similar to digestion in animals. Most CPs actually release digestive enzymes. Some CPs rely on microorganisms such as bacteria to break down the prey into more easily absorbed substances.
Some experiments have shown that CPs can grow without trapping and digesting animals. Other experiments have shown that small amounts of fertilizers can be substituted for live animals, though the plants do not grow as well as those in the wild. Such plants grow poorly, are prone to disease and do not reproduce well. It seems the best way to grow CPs is to let them lure, trap and digest their own prey by their own means, without human assistance.
It is interesting to note that CPs attract insects for two distinct purposes: pollination and nutrition. In both cases scents may be used, as well as ultraviolet pattern techniques that "bull’s eye" key flower or trap parts. This is not surprising since flowers and traps are both modified leaves. Pollinators and prey are often different species.
Many people say that they have tried to grow Venus Flytraps (or other CPs) and that the plants just died. The reason for this is often because tap water was used. If a few simple, but strict requirements are met, it can be quite easy to grow any CP. First of all, be sure to use rainwater or distilled water. Normal tap water is too hard and contains minerals that burn out the CPs roots in a matter of a month or so. Second, use mineral-free soil, not regular potting soil, which again contains root burning minerals or fertilizers. An excellent CP soil mixes equal parts of sand and Sphagnum peat moss. Third, keep the soil wet at all times by standing the pots in a tray constantly filled with rain water. Fourth, do not over feed (over fertilize). This will burn out the plant as surely as an overdose of fertilizer would for a normal plant. If the plants' nutrient-free habitat is kept in mind and the grower tries to reproduce these conditions, he/she will have much better results. More on the details of growing CPs can be found in the section "Growing Carnivorous Plants."