[Corky]

Hi there.
I've got some pots in my polytunnel that had quite a lot of white mould on the surface of the soil yesterday evening. I took this photo today when it has drastically scaled back:



Is this a sign of over-watering? Is the mould harmfull in any way?

I guess that pots in polytunnels need less watering due to the humid air in there, is that right?

Cheers for any replies.

[The Garden Shop]

This i a fungus and can harm young seedlings, but is generally not too much to worry about.
There are a number of things that you can do to prevent this problem in the first place.
The first is to use clean and sterilized plant pots for sowing in polytunnels, and also use fresh, new potting compost.
The second thing to do is keep your polytunnel well ventilated; keeping the doors open during warm summer days - the extra breeze strengthens young seedlings

Another suggestion would be, if possible, water your plants from beneath. This avoids excess water sitting on the top of your soil. Fungi like heat, humidity and still, calm air.
I hope this helps.

[Corky]

Thanks for the reply. I hadn't know that fungus could be passed on using old pots, but of course it makes perfect sense now that you say it. When you say "sterilized plant pots", would a quick dip in some boiling water do the job, or are you thinking of something else?

I'm keeping the tunnel open during the hot days at the moment and things are looking better now. Thanks too for the tip about watering from below.

[The Garden Shop]

From the picture it looks like your using plastic pots. The best way to sterilize them is to soak them in water and bleach for about 10 -15minutes

First remove the worst of the dirt and compost and soak them in a solution of 10 parts water 1 part household bleach

That would be enough to kill off your fungus problem.

So no need even for boiling water, and the bleach and water solution can be reused...

Good luck

[Corky]

Brilliant stuff - thanks so much for your help