When I had an unheated sunroom, the mildew and botrytis would be terrible. I sprayed once a week with a mix of horticultural oil and baking soda. I forget how much oil, whatever the label recommendation is, plus 1T per gallon of baking soda. You won't want to use the oil inside the house ... just because you don't want to spread oil all over! but the baking soda is the main thing for fungi, the oil is a spreader-sticker and doubles as insecticide for aphids and scale.

Nope, no search anymore. Used to be, on all the forums, doesn't work worth a dam anymore on any of them that I've tried.

Each time you open a forum, the search function is at the bottom of the page.

The results you get rely on using the "correct" search word(s). The problem, at least in part, is that few folks use the same words to explain things.

If your mildew is on the soil surface, reduce your watering. Our low light levels allow you to let houseplants go drier than you would in other climates.

I agree. Could also be that you're letting it sit in the water that drains after each watering? Maybe a combination of overwatering/ poor drainage/ highly organic soil. What type are you using?
It's not the real solution because the problem is bigger, but a band-aid fix is to spray the surface with cammomile tea. It'll kill the mildew and it's good for the plants.
- Tom

most of my houseplants are african violets in self watering pots, so yeah, in a sense they are sitting in water. I guess I could stop using the water reservoir and wait until they dry out to water them manually - it's not as if they're likely to bloom this time of year regardless!

If the mildew on the soil or the leaves?

They aren't likely to bloom much here without artificial light. They do well under fluorescents. They do need more light here than in other areas of the country.

They'll bloom in the summer where they are, which is enough for me. The foliage is pretty enough on its own that I don't need blooms year round.

The first mildew I was was on a hoya, and it was on a stem. The hoya is on the same shelf as the AVs, so I imagine it's only a matter of time before I see it on the AVs, too.

It was said: "If your mildew is on the soil surface...."

If it's on the soil surface, it's *not* mildew. Instead, it's soluble stuff from a combination of the potting mix, the applied water, and any fertilizer which has been added.

Further, it signals that it's past time to re-pot into fresh potting mix.

I have a garden room which is part of the house. I keep a fan going 24/7 and it keeps the mildew at bay. I had the temperature too low and noticed that mildew was forming even with that going so I have warmed the room up and added another fan. btw, I also use a fan 24/7 in my cool G/H and don't have a problem with mildew there either. It is a fan that has a heater and when the temp gets too low, I turn the heater on, otherwise, just use it as a fan.

Are you sure it isn't mealy bugs? Hoyas get them often.

Potting soil that is too wet certainly can grow mildew or more properly fuzzy gray mold on the surface. Looks just like mold on bread.

Jean you're wrong about mildew not growing on the soil surface, but on everything else I think you may have hit the nail on the head.
These are African violets kept constantly moist and watered mostly from underneath. It's the constant evaporation without surface flushing that keeps lifting water to the surface, but all the dissolved minerals can't fly away like the water vapor can, and are left behind in a white chalky dust-like covering on the soil that can look like mold. Not hairy like real fungus but chalky/dusty/splotchy looking.
Violetta if you look close & see that's what you have then it probably is time to repot like Jean said. In the future, flush those plants well at least once a month without reusing the the drainage water. Water filters & purifiers help too if you have hard water.
- Tom

These are some fantastic suggestions! Thanks everyone!