Down to Earth: Explore the carnivorous side of gardening with Venus flytraps – Roanoke Times (blog)

The topic of today’s article comes from my son, who, like 9-year-old boys everywhere, is fascinated by the strange and weird. When it comes to the plant world, that means the Venus flytrap.


His interest led to a little research, through which we discovered that the Venus flytrap is native to select boggy areas of North and South Carolina. I had no idea this plant’s native habitat was so close to home. Of course, because the public’s attraction to these plants has resulted in over-collection and endangerment, they now are grown primarily in greenhouses.

If you have a child of your own at home, or if you’re a child at heart, here’s an opportunity to explore the carnivorous side of gardening.

The trap at work

Like other carnivorous plants, a Venus flytrap derives some or most of its nutrients from consuming insects. The plant must attract, capture and digest prey, while discriminating between food and non-food.

These plants don’t have a nervous system or complex muscles and tendons to grab food, chew it and process it. Instead, the Venus flytrap relies on a specialized set of leaves that serve as both mouth and stomach.

Just like some non-carnivorous plants produce attractants for bees, butterflies and other insects, a Venus flytrap secretes a sweet nectar that lures insects searching for food. This nectar is located inside the leaves that form the trap.

When an insect lands or crawls on the plant’s open leaves, it touches short, stiff hairs on the trap’s surface called trigger hairs. If two hairs are brushed in close succession, or if one hair is touched twice, the leaves close down to trap the insect. Scientists still don’t know exactly why this happens.

Even though it lacks a brain, the plant has developed a process for deciding if an object in the trap is edible. Although the trap shuts in less than a second, it doesn’t close all of the way at first.

An insect that’s caught inside the partially closed trap will thrash about in an attempt to escape, and in doing so, will touch one or more of the trigger hairs, signaling the trap to fully close.

An inanimate object, such as a stone, twig, or pencil placed by a child, will not move and tweak the trigger hairs. With no further stimulation, the trap stays partially shut for about 12 hours, and then spreads open again.

To make sure that caught insects are kept in the trap, the edges of the leaves have finger-like cilia that lace together when the leaves shut, forming an air-tight seal. These cilia are what make the plant look like it has spiny teeth, another characteristic that is very appealing to the average child.

How it eats

Once the insect is firmly in the trap, the digestive process can begin. Just like our stomachs, a Venus flytrap secretes acidic digestive juices from the glands in the inside surface of the trap. The insect is digested and nutrients are extracted, usually in about five to 12 days.

The time it takes to reopen depends on the insect’s size, the temperature and the age of the trap. An older trap may secrete a weaker mix of acid and enzymes, resulting in a longer digestive period. Digestion continues until all that’s left of the insect is its hard exoskeleton. The trap reopens and the insect’s remains are washed away by rain or blown away by wind.

The ideal size for insects trapped is about one-third of the trap’s size, which is at most about an inch long. If an insect is too large, the trap won’t be able to form a seal tight enough to keep bacteria and mold out. If bacteria and mold begin growing on the decaying insect, it will infect the leaves of the plant as well, causing rot and, eventually, the loss of the trap.

A plant can tolerate losing a trap every once in a while as it will eventually sprout new ones. Nature has engineered traps to be good for about 10 to 12 partial or complete closures; after that, they lose the ability to trap anything. The leaves remain open and the trap devotes its energy to the process of photosynthesis for the remainder of its life span, usually around 2 to 3 months.

How to grow flytraps

The Venus flytrap is one of the easiest carnivorous plants to grow, which makes it an ideal project for children. It will grow about 5 inches tall, with about 4 to 8 traps per plant.

The basic rule for growing Venus flytraps is to mimic the conditions of their native habitat, which means that they need an environment of high humidity, wet roots and poor, acidic soil.

The plant can be grown outdoors in a regular pot in areas with high humidity, but a terrarium is often recommended as the best growing container. A terrarium will retain moisture while letting in sunlight, keeping the air humid.

The soil you choose should be a mixture of peat moss and sand with a nutrient content similar to that of a bog. Don’t let the soil in your pot or terrarium dry out, but don’t over-water either. Keep the roots wet but don’t submerge the plant in water. Do not add fertilizer, as the plant has evolved to thrive in nutrient-poor soil.

If you grow your plant outdoors in a regular pot, it should get enough insects to eat on its own. But if you grow your plant indoors or inside a terrarium, you’ll need to feed it insects.

Two to three small insects, such as houseflies, per month are sufficient during the growing season. Choose insects that can fit fully inside the trap. For indoor plants, you may also need to manually clean out the leftover exoskeleton, as there will be no wind or rain to take care of this chore.

For more conversation about carnivorous (and non-carnivorous) plants, visit my blog at blogs.roanoke.com/downtoearth.

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