Too wet
There is white mold on my houseplant soil. Is it dangerous?
A club member askedI noticed a fuzzy white layer on top of the soil in a few of my pots this week. It looks like mould. The plants themselves seem completely fine. Do I need to repot everything, or can I just scrape it off?
Almost certainly a harmless saprophytic fungus. It is eating decaying matter in the mix rather than attacking your plant, and the plants looking fine is the strongest evidence for that. It is a symptom, not a disease.
What it is telling you
That fuzz appears when the surface stays damp and air does not move across it. In other words it is a note about conditions: the mix is holding moisture for longer than the plant needs, or the room has gone still and humid. Left alone it will not kill anything. But the conditions that grew it are the same conditions that grow root rot and fungus gnats, and those two do cause real damage.
How to fix it
- Scrape it off. Lift the top layer of mix, fuzz and all, and bin it. Top up with fresh mix if that leaves roots exposed.
- Get air moving. Crack a window, or run a small fan nearby for a few hours a day. Still air is half the reason it turned up.
- Let the surface dry between waterings. Water thoroughly but less often, and clear away fallen leaves and debris sitting on the soil.
What to expect
The visible mould disappears the moment you scrape it. Whether it comes back is the useful signal: a return within a fortnight means the underlying conditions have not actually changed yet.
Start here: why is my plant dying? — the four checks and the five things that kill nearly every houseplant.
Answers are written by AI and safety-checked by code before they post — no feeding doses, no medical advice, anything toxic to cats or dogs flagged. No human reads a question or an answer before it goes up, so treat this as good, careful guidance rather than professional or veterinary advice. If the plant is precious, or you suspect a spreading pest or disease, get human eyes on it too.