Answer: Onions prefer to grow in the cooler temperatures of autumn and spring. When the weather gets too hot, they bolt (send up flower stalks), which indicates the plants are putting all of their energy into producing seed, rather than enlarging bulbs. You should always cut any stalks off of onions as soon as they appear. If you don't, the below ground bulbs will deteriorate. If yours have already opened flowers, or are close to opening just leave them alone. The flowers are pretty and you can collect the seeds and plant them in the garden. In the future, I'd suggest planting onion sets in late July or August for harvest in the late fall months, so your onions won't bolt.
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