The problem
Fungus gnats are one of the most annoying houseplant pests because they seem to appear out of nowhere, hovering around the soil and your face with equal enthusiasm. One internet fix suggests crushing eggshells and adding them to the compost to keep the gnats away. It sounds thrifty and natural.
The hack
The theory is that a layer of crushed shell will stop adult gnats from laying eggs and maybe even add a little natural fertiliser to the soil. It’s also the kind of hack people love because it recycles kitchen waste.
The method
Crush clean, dry eggshells and scatter them over the soil in the pot.
The test
The eggshells sit on the surface, looking rustic but doing little more than collecting dust. The gnats remain because gnats are attracted to damp compost, and eggshells do nothing to change that. The problem is that the pieces are too uneven to form a proper barrier, so adults can still get into the compost.
The verdict
Eggshells belong in the compost bin – they are no deterrent to fungus gnats. If you want fewer gnats, dry the surface, trap the adults and tackle the real cause, rather than decorating your soil.