[Darwin.]

I left my onion sets in the plastic bag they came in, the seem to have started to "sweat" and are really damp now, some even have a mildew on them. Do they need to go in the bin, can I compost them or if I dry them out can they still be used?

It's a lot of onions to throw away.

[Greengage]

dump them, onion sets need to be firm to the touch and not have any mildew or damage to them and they should not be sprouted before planting, so start again.

[Darwin.]

That's a pity but if that's what needs to be done that's what I'll do.

[Dirt Digger]

Agree with greengage; cut your loses, if you don't begin with optimum stock, you cant really expect optimum outcome!!!!

[sgmgarden]

This is a real shame but I am afraid you will have to bin them. There's always time for you to start again though. Good luck