Do Onion Plants Flower?

The portion of the onion you eat is the bulb of the plant where nutrients and water are stored. Like any bulb, onions will flower if the conditions are right. Onions have an attractive ball-shaped cluster of flowers similar to the flower of other members of the Allium family. However, when the plant flowers, this takes away energy from the bulb. To grow large onions, you must control flowering.

A biennial is a plant that starts as a seed and grows during its first year and then continues to grow, flower and go to seed in its second year. Biennials include garden plants such as foxglove and hollyhock and vegetables like beets and celery. As a biennial, an onion shouldn't flower until its second year, but in some cases, flowering can occur in the first year of growth.

The sign for an onion to flower is a change in weather. Normally, the onion grows, goes dormant when the weather cools in the winter and then flowers when the weather warms. However, if the weather during the growing season fluctuates from warm to cool, the plant can go dormant in the first year. When the weather warms again, the plant's system reads this as a signal to come out of dormancy and flower.

You can't stop the onion from flowering once it starts. If you want to eat the onion, pull it and use it as soon as possible. Because the green flower stalk within the bulb will rot, the onion can't be stored. Another option is to leave the flower. The onion makes an attractive white or purple pompomlike flower that brings bees to your garden.

Walking onions are the exception to the rule for not letting onions flower. When the walking onion grows, it develops a flower stalk. As the flower matures, small bulbs form. These little bulbs weigh down the flower stalk until it finally falls over. The bulbs then take root in the soil. Walking onions aren't typically used for a storage onion. Instead, pull up a few young plants to use for green onions.