Venus flytrap

About this plant

The Venus flytrap is a small perennial that grows as a rosette of leaves from an underground stem. John Ellis published the name in 1768; the genus honours Dione, mother of the goddess the Romans called Venus. Each leaf ends in a two-lobed trap fringed with stiff bristles and carrying three sensitive hairs on each lobe. Touching the hairs twice in quick succession snaps the trap shut in under a second; the double touch stops rain and debris from wasting a closure, and the second touch must come within about 20 seconds. The plant keeps counting after that: two signals close the trap, and only continued struggling by the prey, several more touches, switches on the glands that release digestive fluid. The trap then seals for anywhere from a few days to around three weeks before it reopens and the dry husk falls away. A trap closes only a limited number of times, around half a dozen, before it stops working as a trap, though the leaf keeps photosynthesising, and a trap usually digests just one to three meals before it blackens. Triggering traps for entertainment wastes them.

Despite the name, the wild diet is mostly crawling animals. In North Carolina, spiders, beetles and ants are the commonest prey, while the bees and other flying insects that pollinate the flowers are rarely caught.

In the wild the species is confined to a small region of the Carolinas, where it grows in open, nutrient-poor, seasonally wet sand that is kept free of shading shrubs by periodic fire; plants decline where the habitat does not burn roughly every five years, and this small area holds the richest carnivorous plant community in the world. Historically the range ran along the coastal plain from Beaufort County, North Carolina, to Charleston County, South Carolina, and it is now much reduced. Introduced populations have naturalised in the Florida panhandle, southern New Jersey and northwestern Washington State. Wild populations are threatened by habitat loss and by poaching, which has been a felony in North Carolina since 2014, and the species is assessed as Vulnerable on the IUCN Red List (assessment from 2000). In 2023 the US Fish and Wildlife Service decided that federal listing was not warranted. Plants in cultivation are propagated commercially and there is no need to buy wild-collected plants.

Light

This is a full-sun plant. Outdoors it wants the brightest spot you have for most of the day. Indoors, a windowsill alone is rarely enough in temperate latitudes; a dedicated grow light a few tens of centimetres above the plant for 12 to 16 hours a day in the growing season makes the difference between a plant that survives and one that thrives. Red colouring inside the traps is a sign of adequate light, though all-green cultivars exist and some clones colour less than others.

The flytrap is sometimes sold as a windowsill plant that will manage on a few hours of direct sun. It is not a good windowsill plant: full sun means six or more hours. Less light is survivable, but the plant will be smaller, greener and weaker.

Water

Use water low in dissolved minerals: collected rainwater, distilled water, or reverse-osmosis water. Most tap, well and bottled mineral waters carry enough dissolved salts to damage the roots over a few months. Growers who measure their water commonly aim below about 50 parts per million total dissolved solids; tap water under about 90 ppm is acceptable.

During the growing season the simplest method is the tray method: stand the pot in a saucer with a centimetre or two (around half an inch) of water and let the plant draw it up. Keep the water level more than 5 cm (2 in) below the soil surface, which in practice means a tall pot and a shallow tray; the flytrap resents a permanently waterlogged root zone more than most carnivorous plants do. Let the tray dry briefly between refills rather than keeping the pot permanently submerged. In winter keep the medium damp but not wet.

Growing medium

Venus flytraps need an acidic, nutrient-free, well-aerated medium. The standard mixes are sphagnum peat moss with washed silica sand or perlite in roughly equal parts, or pure long-fibre sphagnum moss. Avoid anything with added fertiliser, lime or compost. Perlite and pumice can carry salts, so rinse them thoroughly, keep perlite to about a fifth of the mix, or use sand instead. Use a tall pot where you can; the roots grow deeper than the small rosette suggests.

Temperature

Warm summers suit the plant, and brief spells above 35 °C (95 °F) are tolerated if the medium stays moist. Winter should be cold: a period of roughly 0 to 10 °C (32 to 50 °F) is ideal, and plants in the ground or in large pots survive light frosts and short freezes. A fully dormant, protected plant can survive being frozen solid for about a week provided it does not dry out, and the species is hardy in USDA zones 7 to 10, or 5 and 6 with winter protection. In mild climates an unheated porch, garage window or cold frame works. Hard freezes of the pot itself can kill the rhizome, so insulate or move small pots in severe weather.

Dormancy

From late autumn, as days shorten and temperatures fall, growth slows, traps blacken and the plant retreats to a tight rosette of small leaves. This rest lasts about three months. During dormancy the plant needs little light and only enough water to keep the medium damp.

Give this rest every winter; plants kept warm on a windowsill year-round tend to decline over a few years. Plants under strong artificial light indoors can be grown continuously, but for a windowsill plant, give the rest. See the dormancy lesson for how to provide it in different climates.

Feeding

A flytrap grown outdoors feeds itself. Indoors, you can offer a live or freshly killed insect, such as a fly, small cricket or rehydrated dried bloodworm, to one or two traps every few weeks in the growing season. Prey should be no larger than about a third of the trap, so the trap can seal. Dead or dried food does not move, so after the trap closes stroke the outside of the lobes gently for a minute to mimic a struggling insect; without that stimulus the trap reopens without digesting. Do not feed meat, and do not fertilise the medium; mineral salts in the root zone are what the plant’s whole lifestyle avoids. Feeding is a supplement; light does far more for the plant.

Some growers spray a dilute foliar fertiliser on the leaves once or twice a month for plants grown indoors or under glass. Fertilising a flytrap is a good way to lose it; feed the traps instead.

Repotting

Repot every one to two years in late winter or early spring, as dormancy ends, into fresh medium. This refreshes the mix before salts accumulate and lets you divide clumps that have formed several growing points. Handle the white rhizome gently and plant it with the growing point just at the surface.

Common problems

Blackening traps worry new growers most, and most of the time they are harmless: each trap has a limited life, and in autumn many die back at once. Judge the plant by whether new leaves keep coming from the centre. If the plant is also shrinking in midsummer, look at light and water first. When tidying, snip dead leaves off with scissors rather than pulling them, because a freshly blackened leaf is still firmly attached and tugging it can lift the whole plant out of the pot.

Flower stalks appear in spring. Flowering takes energy, and many growers cut the stalk once it is a few centimetres tall unless they want seed. A plant that flowers and then declines was usually weak before the flower.

Aphids, spider mites and a black-spot fungus are the pests and diseases to watch for. Aphids twist and deform the new leaves in spring; spider mites appear in hot, dry air; black spotting spreads in wet, still, humid conditions and is best met with airflow and the removal of affected leaves. Do not use insecticidal soaps or aerosol sprays on carnivorous plants.

Species-specific notes

The plant changes shape through the year. In spring, as the flower stalk rises, wild-type plants produce leaves with long, narrow, upright petioles that hold the traps clear of the ground, while the autumn and winter leaves are short, broad and flat. Petiole length also varies between clones, and some cultivars never make the upright summer leaves. Grown from seed, a plant takes about five years to mature on its own catches, or two to three years with regular feeding.

Venus flytraps are sold in many named cultivars that differ in colour, trap shape, bristle length and size, from plants with no red pigment at all to plants that are burgundy throughout. Their care does not differ meaningfully. Plants bought from supermarkets in sealed plastic domes are often etiolated and waterlogged; remove the dome, move the plant to strong light and change to pure water, and expect a few weeks of adjustment.