Fungus Gnats in Houseplants
If tiny, mosquito-like insects are flitting around your plants or skittering over the soil, they're almost certainly fungus gnats. They're one of the most common pests of indoor plants. The good news: for established houseplants they're mostly a nuisance, and they're a clear signal you can act on.
What fungus gnats are
Fungus gnats (Bradysia spp.) are small, dark-colored flies with long legs and antennae. They are often mistaken for fruit flies, but unlike fruit flies, they are drawn to moist soil rather than ripening fruit. The adults fly around; the larvae live in the top layers of soil, where they feed on organic matter, fungi, and sometimes fine root hairs.
Established plants are usually harmed very little, but large numbers of larvae can weaken young plants, seedlings, and cuttings, and can cause damage that lets harmful pathogens in.
Why they show up
1. Soil kept too wet
Fungus gnats thrive in damp potting soil. Consistently wet soil — especially heavy, waterlogged mix with decomposing material, algae, or extra organic matter — is a breeding ground for them. Overwatering is the real culprit.
2. They get brought in
Fungus gnats typically enter homes through contaminated potting soil, newly purchased plants, or open doors and windows.
How to tell them from fruit flies
- Fungus gnats are small and dark with long legs, and they hover low over the soil.
- Fruit flies are attracted to ripening fruit and the trash, not houseplant pots.
- If the flies are in the pot, the soil is moist, and the problem lingers near plants, they're fungus gnats.
How to get rid of them
1. Let the soil dry out. The single most important step — fungus gnats need consistently damp soil to breed. Let the pot dry more between waterings and make sure it drains and never sits in water. 2. Use yellow sticky traps placed just above the soil to catch the flying adults and monitor the population. 3. Stick to dryer, less organic-heavy conditions and avoid overwatering long-term so the gnats don't return.
Combining drier soil with sticky traps breaks the cycle. Because established plants suffer little harm, you don't need to panic — you just need to correct the watering and reduce the population.
Preventing fungus gnats
Fungus gnats are far easier to prevent than to eliminate. The key is to avoid keeping potting soil constantly wet — let the top of the soil dry between waterings and make sure pots drain and don't sit in water. Check new plants and new bagged potting soil for gnats before bringing them into your collection, since that's how the problem usually arrives. And remember: the flying adults are mostly harmless to established plants, so fixing the damp soil is what actually ends the problem for good. With drier soil and a little patience, fungus gnats clear out within a few weeks — and stay away as long as you don't let the pots get waterlogged again.
Related plants
- Peace lily — kept moist, so commonly affected
- Monstera — enjoys humidity, so watch the soil doesn't stay wet
- Pothos — easy to overwater