Carnivorous plants come from bogs and other places with almost no nutrients in the ground. That's why they catch insects. It's also why the things we do for every other houseplant kill them: tap water, ordinary compost and plant food. If your flytrap or sundew is slowly blackening, the cause is almost always one of those three. The fix is to do less, with purer ingredients.
01At a glance
- Water: rainwater first, distilled water second. Not tap water, and not bottled mineral water.
- Compost: a peat-free carnivorous mix or sphagnum moss. Never ordinary potting compost or garden soil.
- Feed: none. Most carnivorous plants need no fertiliser at all.
- Light: as bright as you can give. Weak light gives green, floppy traps.
- The exception: the tropical pitcher plant (Nepenthes) shouldn't sit in a deep tray of water.
02Water: why rainwater matters
Tap water carries dissolved minerals. A normal houseplant shrugs them off. A bog plant can't, and the RHS warns that tap water, especially in hard-water areas, can kill a Venus flytrap. The minerals build up in the lean compost over months, so the decline is slow and easy to blame on something else.
Collect rainwater in a clean butt or bucket, and keep a bottle of distilled water for dry spells.
### The tray method (flytraps, sundews, butterworts, Sarracenia)
- Stand the pot in a saucer or tray of rainwater during the growing season. The RHS suggests up to 2.5cm deep.
- Top the tray up before it runs dry. Sundews and flytraps are bog plants and shouldn't dry out while growing.
- In winter, ease off. Water from below, then pour away what's left in the saucer. Butterworts want less again: the Carnivorous Plant Society keeps Mexican kinds dry through their winter rest.
### Tropical pitcher plants are different
The tropical pitcher plant is a jungle plant, not a bog plant. It still needs rainwater, but the Australasian Carnivorous Plant Society advises against standing the pot in a water tray, as it can lead to root rot. Water from the top, keep the mix moist but never soggy, and let it drain. If you want more humidity, stand the pot on pebbles above the water rather than in it.
03Compost: lean, not rich
Ordinary compost is far too rich. The RHS says never plant carnivorous plants in soil or potting compost.
- Easiest: a ready-made peat-free carnivorous compost.
- For Sarracenia, the RHS suggests 75% sustainably produced sphagnum moss with 25% finely sieved pine bark, or sphagnum moss on its own. Flytraps also grow in live sphagnum.
- For Nepenthes: a looser, airier mix. Clemson Extension suggests roughly 60% sphagnum moss, 20% perlite and 20% orchid bark.
- Don't rush to repot. The RHS advises keeping a new indoor plant in its original pot and compost for at least the first year.
04Feeding: let them hunt
The RHS is clear that most carnivorous plants need no additional fertiliser. Never add plant food to the compost. On a windowsill they'll catch fungus gnats and small flies on their own, and that's plenty.
- Don't feed them meat or cheese. The RHS points out that flytrap traps only digest prey that moves inside them. Anything else just rots.
- Don't spring the traps for fun. The RHS says a trap can close only around three times before it dies.
- Nepenthes indoors: if it never catches anything, an occasional small insect dropped into a pitcher is enough. Clemson describes a very weak feed on the leaves and into open pitchers, and the Australasian society warns overfeeding can stop pitchers forming. Never feed into the compost.
05Light: the other half of the job
Most of these plants want far more light than people expect. The RHS says full sun helps a flytrap thrive and colour its traps red, and poor light gives weak, straggly traps.
There's one caution. The RHS notes that leaves can scorch in direct sun through glass. On a south-facing sill in high summer, watch for bleached or browned patches, and if you see them, move the plant back a little.
The tropical pitcher plant wants bright light without harsh midday sun. Clemson suggests an east- or west-facing window, and humidity is what gets it making pitchers.
06Mistakes that kill carnivorous plants
- Tap water "just for a few weeks". The minerals stay in the compost and the damage builds up.
- Repotting into multipurpose compost.
- Keeping a flytrap warm all winter. It needs a cooler rest. Our Venus flytrap profile explains how.
- Giving a Nepenthes a cold winter rest. It's tropical and keeps growing all year.
Before placing them where children or pets can reach, check the safety flags on our sundew, butterwort and tropical pitcher plant profiles.
How we checked this
Every care and safety claim on this page is verified against horticultural and veterinary sources.
Sources: RHS — How to grow carnivorous plants · RHS — Venus fly trap · Clemson Cooperative Extension — Tropical pitcher plants (Nepenthes spp.) · Australasian Carnivorous Plant Society — Nepenthes · Carnivorous Plant Society — Pinguicula growing guide
Checked 8 October 2026. If our advice ever conflicts with the RHS, believe them and tell us.