If you’ve noticed tiny black flies flying around your houseplants, you’re not alone. Fungus gnats are one of the most common pests we hear about from houseplant gardeners—and they can seem to appear almost overnight. The good news is that fungus gnats are usually more of a nuisance than a serious threat to established houseplants. The key to controlling them is understanding where they come from and what their larvae are doing in the soil. What Are Fungus Gnats? Fungus gnats