This Pretty Houseplant is Fantastic at Killing Fungus Gnats – Yes, Really

September sees the return of fungus gnats, but there’s a very easy, very lovely way to control them: grow a butterwort as a houseplant and it'll eat them all up. Butterworts are carnivorous plants that produce a sticky dew on their leaves to trap flies, and clumsy fungus gnats are easy prey. And that’s a real relief for us indoor gardeners right now, as the end of summer is peak time for pesky little sciarid flies that breed in houseplant soil. So, rather than reaching for yellow sticky fly traps from Amazon to control those annoying houseplant flies, grow a pretty little butterwort instead.

Butterworts – or ‘pings’ as they’re often called on account of their Latin species name, Pinguicula – are small houseplants so they’ll fit alongside your current plant collection. Leaves grow in neat rosettes with a sticky coating that gives the plant a silvery, sparkling appearance, and tiny flowers grow on slender stalks in spring or summer. Get a few basics right – all explained below – and butterworts are simple to grow, and as plants grow bigger, they'll even gobble up mosquitoes.

And really, which would you rather see on your windowsill?

Pick a Mexican Butterwort

While all butterworts are carnivorous, not all are created equal when it comes to catching fungus gnats. If you're serious about ridding your houseplants of sciarid flies, then Mexican (also called tropical) butterworts make far better living flypapers than North American butterworts. Mexican butterworts form rosettes of wide, flat leaves with lots more horizontal landing space for gnats than North American butterworts, and they’re far easier to grow, too. While North American butterworts require humid conditions to grow well and are prone to rotting, Mexican butterworts are far more resilient and will happily sit on a windowsill without much TLC.

Look for Pinguicula cyclosecta, also known as the purple-leaf butterwort on account of the lavender tone its leaves can develop, which has pretty deep violet-purple flowers. Mexican butterwort Pinguicula cyclosecta is available from the Bloomify Store via Amazon. Another Mexican butterwort is Pinguicula esseriana, also available from the Bloomify Store via Amazon. This has pale green, pink-flushed leaves and paler lilac-hued flowers. Both grow to 4 inches high and wide.

How to Care for Mexican Butterwort

Butterworts evolved to extract nutrients from trapped flies because they grow in very poor soil. Replicate this with a potting soil designed specifically for carnivorous plants such as Professional Carnivorous Plant Soil from the Leaves and Soul Store via Amazon. This is vital – use standard potting soil and your plant will probably die.

Just as essential is to irrigate your butterwort with rainwater or distilled water such as Parent’s Choice Distilled Water from Walmart. Tap water contains minerals which will build up in the potting soil and kill your butterwort. It’s best to keep the soil just-damp by standing the pot in a half-inch-deep saucer that you keep permanently topped up with water. That way, the plant will wick just the right amount of water it needs.

A Mexican butterwort is easily scorched by strong midday sun but needs a few hours of gentle sunlight to produce plenty of the fly-trapping sticky dew. Direct sunlight will also bring out the pretty pink or purple foliage colors, so choose a warm windowsill that gets morning or evening sun but is cast into shade through the central part of the day.

If you want to use your butterwort to keep shady houseplants gnat-free, a full-spectrum LED grow light will work just as effectively as sunlight. This needn’t be expensive, as this $13 programmable halo grow light from Walmart proves.

How Effective are Butterworts at Controlling Fungus Gnats?

These carnivorous plants will only deal with the adult fungus gnat population and for every sciarid fly you see flying around, there will be hundreds more larvae in the soil. To break the gnats’ lifecycle, you’ll also need to deal with the larvae and maggots that hatch from eggs laid just under the soil surface of your houseplants. Use a natural soil drench that targets larvae like FGX from Amazon. Another smart move is to reduce fungus gnats by sprinkling cassia cinnamon on houseplant soil as its anti-fungal properties help to remove the maggots’ food source in the soil.

Butterworts can enter a state of dormancy over winter, though Mexican butterworts are less quick to nap than North American species as long as they're kept warm enough. During dormancy, the rosettes shrink to the size of a coin and leaves lose their stickiness. There’s no need to worry though – just reduce watering and increase it again once you see signs of growth in spring, and your butterwort will be just fine. Because fungus gnats are most active in September and October and again in April and May, dormancy won’t affect the plant’s performance as a living fly trap.

Butterworts are also fantastic at catching whiteflies, those tiny sap-sucking bugs that can infest the undersides of houseplant leaves and quickly breed in greenhouses. Many folk grow butterworts in their greenhouses to help control whitefly, but you’ll need to make sure you shade plants from strong sunlight.

Mexican butterworts are simple to propagate by leaf pulling, so you can quickly and easily expand your carnivorous collection to give houseplants more protection from fungus gnats. Bye bye sciarid flies!