[lordthanatos]

Might be tricky without pics but some i have  put my onion sets into modules about 2 week ago in a heated greenhouse. I have watered them twice ( lightly) . Now most of them have a white powdery mold around the base. I have pulled a few out and the roots are growing very well and most have now have green shoots. Should i be worried or do they need binning?thanks

[AlaninCarlisle]

Interesting question and I'd love to read other views on this as I have never heard of onion sets being started in a heated greenhouse before. I always put sets direct into the ground around early March and start any ones from seed in a propagator in January for onward planting into modules in an unheated  greenhouse, again around now.

[lordthanatos]

Well i say heated more like just kept above zero lol i thought it could be cause it was so cold and damp in the greenhouse

[New shoot]

If they are growing roots and shoots I wouldn't bin them. 

Can you gently rub the mould off to stop it spreading?  I would try that and see how they go 

[JayG]

I've noticed that even multipurpose composts can grow a layer of white mould on the surface under certain conditions - if it's not confined to just the bulbs they'll probably be fine.

When it happens to my young plants (not onion sets) I usually disturb the soil surface to break it and the mould patches up a bit (not saying it's a cure but it makes me feel better!  )

Ah, New Shoot seems to be thinking something along the same lines. 

[lordthanatos]

I did wonder if the compost but its just on the sets at around soil level? Yeah the one i pulled have a very good set roots on it

[I Love Spuds]

If you have healthy roots and no sign of rotting then I would say carry on. I have had stuff with mildew on it grow on healthily, although I did pot up later which removed the mildew, or at least buried it!

[New shoot]

Is it fresh compost, or stuff that has been sitting around a while?  I sometimes get a fine layer white mould on the top of my compost bin if its been there a while.  I keep mine in a galvanised dustbin just outside the greenhouse door. 

Looks like the consensus is that they will be fine either way 

[lordthanatos]

Actually yes its last years left over compost so may be that. Ok thanks for help folk