Newbie advice on onion sets

Regardless of how many come in a bag, I always find quite a few already rotted or dried out, which lowers the viable amount. If you have extra once yours have sprouted, then exchange with someone who doesn't have onions for something you can use. It's a good way to make friends.

I bought a load from Wilkinsons on Sat and tried to estimate how many there are by weighing the bag and then weighing a sample of sets - I estimate it at over 100 in a 500g bag. As Trillium suggests they will not all be good. I would sort the biggest healthiest looking ones to plant as onions and either pass on the rest or plant close together as suggested by Fisherman. The ones I bought were only about £1.27 so you will not be risking too much either way.

Thanks everyone for the advice when would be the best time to plant and also how long will the sets keep for!

If you have a nursery nearby, I would highly recommend that you check them out for "Centurion". I grew them last year and they were the best onions I'd ever grown. £1.97 a kilo from my local.