Venus flytrap

Identification and origin

Dionaea muscipula belongs to the family Droseraceae, the sundew family. It is endemic to a small part of the southeastern United States: the coastal plain of southeastern North Carolina and a small neighboring area of northeastern South Carolina. There it grows in longleaf pine savannas, on sandy, wet, very nutrient-poor soils. It is a temperate perennial that experiences real winters.

The plant forms a low rosette 6–12 in tall and up to 12 in wide. Each rosette has six or more leaves: a flat green leaf stalk ends in a hinged trap about 1 in across, often flushed pink or red inside and edged with stiff bristles that interlock when it closes. The species name means “little mousetrap.”

The trap shuts when prey touches two of the six trigger hairs on its inner surface. Substances released by the insect then set off the flow of digestive enzymes; once the nutrients are absorbed, the trap reopens. Digestion takes anywhere from a few days to several weeks. In spring, a leafless stalk 4–12 in tall carries clusters of small, white, cup-shaped flowers about 1 in across, each with five petals.

The species is threatened in the wild: collecting it there is illegal, and it is listed in Appendix II of CITES. Buy only nursery-propagated plants. Many cultivars differ in trap size, color, or bristles: ‘Red Dragon’, which turns red in full sun; ‘King Henry’, with large chartreuse to yellow traps; ‘Dente’, whose bristles look like shark teeth; or ‘Justina Davis’, which stays green because it makes no red pigment.

Light

Light is the key to success. It needs at least six hours of direct sun a day, ideally behind a south-facing window. An ordinary windowsill is usually too dim: a weak, leggy plant is almost always short of light. A horticultural LED light, left on 12 to 16 hours a day depending on the size of the plant, is a useful supplement to sunlight, especially in winter. Under artificial light alone, plan on about 14 hours a day of strong white light.

In bright light the plant takes on red tones; in shade it stays green. Outdoors, full sun suits it; in hot, dry climates, give it morning sun and part shade in the afternoon.

Watering

The mix must stay moist at all times without being soggy. The most reliable method: a pot with a drainage hole set in a saucer holding 0–1 in of water, which wicks upward. Keep at least 2 in between the water level and the surface of the mix, and never let the saucer dry out. Watch the saucer rather than a calendar: it empties faster in hot weather.

Water quality is critical. Use rainwater, distilled water, or reverse-osmosis water. Tap water, and even bottled or filtered water, often carries too much dissolved salt and can kill the plant; an ordinary filter does not remove it. If the air is very dry, a ventilated terrarium helps; closed, it overheats in summer.

Potting mix

The mix must be acidic and lean. The classic blend is equal parts horticultural sphagnum peat and coarse horticultural sand. Long-fiber sphagnum alone also works. Avoid perlite, pumice, and any enriched potting soil, which add salts. A layer of pure sand about 0 in deep on top reduces rot in the older leaves and discourages fungus gnats.

Never add fertilizer: it slowly kills the plant. It feeds through its traps. Offer live prey or rehydrated dried bloodworms about once a week or every two weeks, no more than a third the size of the trap, and gently massage the trap so it seals. No meat, and no caterpillars, which can chew their way back out. Outdoors it catches prey on its own.

Temperature

While growing, it is comfortable at 64–75 °F. Keep it away from heating and air currents.

Winter dormancy is triggered by shortening days and reinforced by cold. To provide it, let the light dwindle naturally, gradually lower the temperature to 36–50 °F for at least ten weeks, stop feeding, and keep the mix just barely moist. The leaves blacken: this is normal; cut them off once they are completely black. Growth resumes in late winter. A plant grown year-round under strong artificial light can skip dormancy, but a plant denied rest year after year declines.

In the ground it is hardy in USDA zones 7 to 10; protect it from hard freezes below 19 °F, and never let it dry out in winter.

Repotting

Do not repot a plant you have just bought: its small pot usually lasts it two years. Repot in spring when the rosette reaches the rim or new traps fail to develop, and at least every two years to refresh the mix. Choose a pot with a drainage hole that is fairly tall, about 4 in, to keep the surface well above the water.

Pruning

Cut off black leaves once they are dry: each trap dies after a few meals and is replaced by a new one. Remove the flower stalk as soon as it reaches 1–1 in, unless you want seed, because flowering exhausts the plant.

Propagation

Division is the simplest method: at repotting time, separate pieces that each have a growing point and a few leaf bases. Leaves pulled from the clump and set to root also produce new plants. Sow seed on the surface of moist mix at 68–77 °F; seedlings grow slowly and can take up to five years to mature. Commercially, flytraps are produced by tissue culture.

Common problems

• Pale, floppy plant with small traps: too little light.
• Traps that turn black after a meal: prey too large, leading to bacterial rot.
• Leaves blackening in fall: the plant is going dormant, not diseased.
• New traps that fail to develop: salt buildup, unsuitable water, spent mix, or a pot that is too small.
• Root rot: mix too wet; on the other hand, roots that dry out, even briefly, also suffer.
• Pests: aphids, spider mites, and mealybugs; also watch for black spot.

A single symptom can have several causes: always check light, water, potting mix, and season before drawing conclusions.

Toxicity

No toxicity reported: the Venus flytrap is classified as non-toxic to dogs, cats, and horses. Just avoid setting off traps for fun: each closure costs the plant energy.