What size were the onions when you planted them, Begobligan? Onion sets above a critical size will bloom instead of forming a bigger bulb. Spinach is a cool weather crop, and many varieties will bolt if the weather turns hot and dry. Sometimes it does better if planted in late summer for a fall crop.

Thanks Tugbrethil, the onions were bought in a pack, from a garden centre I can't remenber the breed of them though

Peewee marble size is fine, but jumbo marble size is getting iffy. Jumbo olive size is definitely too big. I've had a few problems lately because the Dutch sets I've been getting from the nursery lately seem to get bigger each year.

Onions will bolt if they get to dry. Inadequate and/or irregular watering causes it!

Thanks, Ian, I forgot that. I'm so used to watering things to a fairtheewell here, I forget how things can be for people who rely on the rain more--when it doesn't arrive!

Thanks evrybody, our allotment does seem to dry out quickly although I water it every morning (unless its raining) but in this part of Lincolnshire we dont get much rain!