"Feed Me Seymour!" Carnivorous Plants All Bark, No Bite

July 25, 2003

WOOSTER, Ohio — In the dark comedy classic “Little Shop of Horrors,” a giant Venus flytrap seeks a steady diet of humans with the help of its florist owner. Likewise, in the sci-fi movie “The Day of the Triffids,” hapless victims fall prey to walking, carnivorous plants. In reality, carnivorous plants are nothing like the monsters Hollywood has entertained us with throughout cinema history. Most grow to only a few inches in height and feed mainly on insects. While some can capture prey as large as small frogs or lizards, carnivorous plants do not feed on humans and are certainly no danger to humans. In fact, feeding them food, like raw meat, will kill them. Bob McMahon, an Ohio State University Agricultural Technical Institute coordinator of Greenhouse Production and Management Technology and chair of the Horticultural Technologies Division, was on hand at BioHio recently to share his love for carnivorous plants, dispel old myths and teach participants how to grow carnivorous plants at home. The three-day event was held on Ohio State’s ATI campus as well as at the neighboring Ohio Agricultural Research and Development Center (OARDC). “Growing carnivorous plants has been a hobby of mine for 30 years, dating back to the 10th grade,” said McMahon, an associate professor. “My dad, who is a medical doctor, was given a potted Venus flytrap as a gift and he took it home and it was love at first sight.” McMahon maintains an extensive carnivorous plant greenhouse collection at ATI. Nearly 600 species and subspecies of carnivorous plants have been recorded, but are generally lumped into three categories based on their trapping methods: spring traps (Venus flytrap); pitfall traps (pitcher plant); and fly paper mechanisms (sundew or butterwort). McMahon said that carnivorous plants have long since fascinated kids and adults alike because of their diversity (they are found on every continent except Antarctica); of their unique environmental adaptation (they primarily are found in Sphagnum moss bogs); and they are generally easy to grow and maintain if some basic rules are followed. “The soils that these plants live in are nutrient deficient. They have adapted the remarkable ability of supplementing their diet with nutrients, such as nitrogen, from insects and other animals,” said McMahon. “In other words, insects serve as a fertilizer to carnivorous plants.” Probably the most easily recognizable carnivorous plant is the Venus flytrap. The plant has a leaf blade modified into a trap that snaps shut with interlocking teeth when insects, in search of nectar, wander inside the trap. Only one species of Venus fly trap exists and grows naturally in one area of the world — near Wilmington, N.C. But the plant is easily propagated and can readily be found in any greenhouse, nursery or home garden center. Pitcher plants are characterized by hollow leaves that collect rainwater, allowing the plant to more easily capture careless insects. “The pitcher plant secrets a digestive enzyme into the water and when the insect wanders too far into the hollow leaf, it slips and falls into the water where the soft tissues are broken down and digested by the plant,” said McMahon. Many species of pitcher plants exist throughout the world. The northern purple pitcher is commonly found in Ohio and grows mainly in sphagnum moss bogs. The butterwort and sundew are also found in Ohio. The plants utilize a flytrap mechanism whereby insects become stuck on their sticky leaves. The leaves may then fold over, trapping the insect and secreting digestive enzymes that break down the soft tissues of the insect. For the homeowner or garden lover looking to try a hand at growing a carnivorous plant, McMahon recommends the following tips: • Do not place plants in regular potting soil. Carnivorous plants require very acidic soils, at least a pH of 4. Dried long-fiber Sphagnum moss, or living Sphagnum moss is sufficient, both of which can be found at garden centers. Another acceptable growing medium is equal parts of Sphagnum peat moss and coarse sand. • Carnivorous plants require pure water — either distilled, rainwater or melted snow. Tap water is full of chlorine, fluoride and calcium that is toxic to the plants. • Carnivorous plants thrive best in direct sunlight — at least six to eight hours of it a day. The leaves and veins of carnivorous plants will turn red under adequate sunlight. McMahon said the red color acts as an additional insect lure. For indoor plants without adequate sunlight, a shop light consisting of two 40-watt fluorescent light bulbs set a few inches above the plant should do the trick. • Most carnivorous plants go dormant during the winter, so homeowners with indoor plants must account for the length of light. From May through September, fluorescent bulbs should be on 14-16 hours a day. After that time, gradually decrease the light to eight hours a day through February or March, and then gradually increase the light back to 16 hours by May. Plants should also be placed on a north-facing window to allow them to chill to around 50 or 60 degrees. For plants grown outdoors during the summer or grown next to a sunny window, the decreasing amount of daylight as fall progresses will naturally induce dormancy for these plants. However, for outdoor-grown plants, especially Venus flytraps and other plants native to warmer climates than Ohio, such plants should be over wintered in a cool room or next to a window so that adequate cooling is received. • Carnivorous plants require a lot of humidity and moisture during the active growing season. To accomplish this, container plants should be placed in a saucer filled with about two to three inches of water. This supplies the moisture the plants need. During winter, the soil should remain damp, not wet. Plants grown in aquariums or terrariums (leave the top open for air circulation so that damaging heat build up does not occur) will receive adequate humidity. • Do not feed carnivorous plants raw meat. Meat contains too much protein and fat, resulting in the rotting of the trap and the meat, damaging the plant. Allow outdoor plants to catch their own meals. For indoor plants, feeding them one or two small living insects about every two weeks is sufficient. They may also be placed outside once a week in a shady area to allow them to catch their own insects. They can also be lightly misted with a very weak acidic fertilizer solution (i.e. one-tenth of the strength recommended for house plants) once a month. During winter the plants do not need to be fed. • Replant every two to three years. Eventually the moss will break down and shrink in volume. The Internet entertains of wide variety of Web sites with information on carnivorous plants and how to grow and maintain them. For more information, contact Bob McMahon at mcmahon.2@osu.edu or call (330) 264-1320.

Candace Pollock
Bob McMahon