Several carnivorous plants trap and digest gnats, making them a natural option for dealing with these pests indoors. The most effective gnat-catching plants are sundews, butterworts, and pitcher plants, each using a different trapping strategy. All of them thrive in the same moist, bright conditions that gnats love, which means they’ll be right where the problem is.
Sundews: The Best Gnat Catchers
Sundews (Drosera) are arguably the most effective gnat killers you can grow at home. Their leaves are covered in tiny tentacles tipped with drops of sticky, glistening mucilage that looks like morning dew. Gnats and other small flying insects are attracted to the shine and sweetness, land on the leaf, and get stuck immediately. Once trapped, the leaf slowly curls around the insect over the course of several hours, pressing it against digestive glands that break down the soft body and absorb the nutrients.
The Cape sundew (Drosera capensis) is the species most commonly recommended for beginners. It catches gnats, fruit flies, and the occasional housefly, grows well on a sunny windowsill or under a grow light, and produces new leaves continuously. Unlike Venus flytraps, which need a specific trigger to snap shut and can only close a limited number of times, sundews passively catch anything that lands on them. A single healthy Cape sundew can have dozens of active leaves at once, each one a functioning trap. For a serious fungus gnat problem, two or three sundews placed near the affected plants can make a visible dent in the population within a couple of weeks.
Butterworts: Subtle but Effective
Butterworts (Pinguicula) work like living flypaper. Their broad, flat leaves produce a sticky mucus across the entire surface, trapping gnats and other small soft-bodied insects on contact. The leaves have tiny hairs that secrete this adhesive, which shimmers in sunlight and produces a faint fungal or moldy odor that actively attracts gnats. Once an insect is stuck, the leaf margins slowly roll inward over the prey, beginning the digestion process.
Butterworts are especially well suited to catching fungus gnats and thrips because their trapping surface is large relative to the size of these tiny insects. They also tend to look less “alien” than other carnivorous plants. Many Pinguicula species resemble small succulents with pale green or violet-tinged rosettes, making them easy to blend in with a houseplant collection. Mexican butterworts (Pinguicula moranensis and related species) are the easiest to grow indoors, tolerating slightly lower humidity than sundews and requiring less fuss overall.
Pitcher Plants: Passive Pit Traps
Pitcher plants use a completely different strategy. Their modified leaves form tube-shaped or funnel-shaped pitchers filled with digestive fluid. Insects are attracted by nectar around the rim, lose their footing on the slippery inner surface, and fall into the liquid below where they drown and are slowly digested. North American pitcher plants (Sarracenia) and tropical pitcher plants (Nepenthes) both catch gnats, though they’re generally better at trapping larger insects like wasps and flies.
For gnats specifically, pitcher plants are less efficient than sundews or butterworts. A gnat can sometimes escape from the rim of a pitcher, whereas it has almost no chance of pulling free from the sticky surface of a sundew leaf. That said, Nepenthes species with smaller pitchers do catch gnats regularly, and they make impressive hanging plants. Sarracenia species need a winter dormancy period with cold temperatures, which makes them harder to keep as year-round houseplants.
How to Keep Carnivorous Plants Alive Indoors
Carnivorous plants evolved in nutrient-poor bogs, and their care reflects that origin. The two things that kill them fastest are tap water and regular potting soil. Both contain minerals that these plants can’t tolerate.
Use distilled water, reverse osmosis water, or rainwater. The general guideline is to keep the total dissolved solids below 50 parts per million. Most tap water ranges from 100 to 400 ppm, which is enough to slowly poison these plants over weeks or months. Water that’s been through a softener is even worse because of the added sodium. Keep the soil consistently moist. Many growers use the “tray method,” sitting the pot in a shallow dish of water so the soil wicks moisture from below.
For soil, the standard mix is a 50/50 blend of peat moss and perlite (or silica sand). The peat must be pure sphagnum peat with no added fertilizer. Check the bag’s ingredient list: it should say 100% Canadian peat or similar. Never use regular potting soil, miracle-gro, or anything with compost or fertilizer mixed in. These plants get their nutrients from the insects they catch, not from the soil, and added fertilizer will burn their roots.
Light and Placement
Sundews and butterworts need bright light to produce their sticky trapping mucilage. A south-facing windowsill works well in most climates, or you can use a basic LED grow light placed a few inches above the plant. Without enough light, sundews lose their dewdrops and butterworts stop being sticky, which means they stop catching anything.
Place your carnivorous plants near the source of the gnat problem. If fungus gnats are breeding in the soil of your houseplants, put a sundew or butterwort right next to those pots. Adult gnats flying out of the soil will encounter the sticky traps before they can spread. Keep in mind that these plants catch adult gnats but don’t address larvae living in the soil. For a heavy infestation, pairing a carnivorous plant with a soil drench (like a diluted hydrogen peroxide treatment for the affected houseplant pots) tackles both life stages at once.
Which Plant to Start With
If your main goal is killing gnats, a Cape sundew is the strongest choice. It’s inexpensive, widely available from online nurseries and garden centers, fast-growing, and catches more gnats per plant than any other option. It produces long, strap-shaped leaves that unfurl continuously, replacing old leaves with fresh sticky ones.
If you want something lower-maintenance and slightly more forgiving, a Mexican butterwort is a close second. It tolerates a bit less light and doesn’t need quite as much water, though it still requires the same mineral-free water and soil. For visual impact and variety, adding a small Nepenthes pitcher plant rounds out a collection nicely, but it won’t catch gnats as reliably as the other two.
Venus flytraps are the most famous carnivorous plant, but they’re actually a poor choice for gnat control. Their snap traps are designed for larger prey, and a gnat is often small enough to crawl right back out between the interlocking teeth of the trap. They also require winter dormancy at temperatures below 50°F for several months, making them finicky houseplants compared to tropical sundews and butterworts.