Plant of the Week
Latin: Dionaea muscipula
There are many plants that avid gardeners know and admire but never attempt to grow. Until recently, that was how I felt about Venus flytrap; cute but not worth the investment of time and energy to keep it alive. But, after stumbling over a display in the central isle of the grocery store, I succumbed to temptation.
Venus flytrap, Dionaea muscipula, is a small carnivorous (insectivorous) bog plant native to the coastal region of the Carolinas. It’s small, forming a rosette of leaves about 6 inches across. In the spring, it sends up a foot tall scape of white, five-petaled flowers.
The leaves are highly modified with the petiole having a pair of flattened, leaf-like appendages that come before the true leaf blade, the trap. The trap is a marvel of vegetative engineering specifically designed to trap flying, soft-bodied insects. The trap is usually red tinged on the inside and an inch or more long. The marginal teeth of the leaf blade are modified into curved, eyelash-like fingers.
Carnivorous plants excite the imagination of children and a dedicated following of plant nerds who go to great lengths to keep these treasures alive and learn their secrets. Charles Darwin, reporting in his 1875 book Insectivorous Plants, is the best known of many scientists who have seriously studied them. Though much studied, the mechanism of how a plant can move so quickly is still not completely understood.
In January 2005, an article by Harvard mathematician L. Mahadevan and his colleagues (Nature, Y. Forterre et al.) provided new evidence to explain how the physical process works. Using mirrors and close-up, high speed photography, the team watched how the trap shape changed as it closed. By marking the leaves with a series of dots they were able to make exacting measurements and develop a mathematical formula explaining the forces involved.
What they demonstrated is that the leaf closes so quickly because of a mechanical snap-buckling mechanism as the outer (lower) leaf surface changes from convex to concave. This occurs in stages with the first phase requiring an insect to consecutively touch at least two of the trigger hairs on the inside of the trap.
When this happens, an electrical signal flashes to a series of elongated cells running parallel to the outside mid-vein of the leaf. These cells change shape and become more inflated, building up pressure on the outside of the trap. This requires about a second to occur. Then, a critical point is reached when the trap springs shut in about half the time it takes to blink your eyes.
Once trapped, insects are digested in about a week by the enzymatic juices produced by the leaf. Then the trap reopens. If you mechanically trigger the trap to close, it’ll reopen in about eight hours. Leaves are good for about three closures, if they catch a bug, before dying. Seven artificial closures are said to kill a leaf. Many carnivorous plants are found in boggy environments where nitrogen is in short supply. They don’t have to live off of the insects they trap in their leaves, but it’s an intriguing means of self preservation.
Venus flytrap is best suited to a sunny, cool area with high humidity. It requires a pH around 5.0, a highly organic potting soil and moist, but not soggy conditions. Oftentimes, it’s
grown in terrariums. Drought, high salts, high rates of fertilization, low humidity and too much fooling around with the traps are not to its liking.
Tissue culture propagation has been perfected for these charming carnivores, so growing them on a sunny windowsill in no way endangers the survival of the plants in the wild.
By: Gerald Klingaman, retired
Extension Horticulturist - Ornamentals
Extension News - February 24, 2006
The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.