Onions in the garden. Birgitta Kullman/Shutterstock.com
And if you see a flower head forming, snip it off immediately before it blooms.
Dig up any onions that produce a flower stem. Once they start to set seed they won’t grow any more, and they don’t store well either.
But onions that have bolted are still edible and will taste fine, so dig them up first and eat them, leaving the others to mature in the ground.
And finally, don’t be disheartened. Professional growers suffer from onions setting seed too. Just use them in the kitchen – you haven’t lost anything.