Gardener tries growing onions from seed instead of sets; results are huge!
Leslie with her onions

Leslie couldn’t be more thrilled with the crop of huge onions she grew from seedlings.

Leslie works with me at Gardener’s Supply and our conversations tend to run toward plants. She’s an enthusiastic gardener, too, with decades of vegetable and flower growing experience. When either of us discovers a nifty new plant or picks up a new gardening tip, we share.

So imagine my surprise last winter when Leslie said that she’d read my post on growing onions and was shocked to learn that onions are biennials. She has always grown onions from marble-sized onion bulbs, called sets, which grew vigorously, but didn’t produce large bulbs. After making the connection between the onion lifecycle and her garden experience, she decided to try growing them from seeds started early this year.

On the advice of another friend who runs a market garden, Leslie bought a collection of sweet, mild onion seedlings from Johnny’s Selected Seeds. Her assortment included three varieties: yellow-skinned Ailsa Craig Exhibition, Red Burgermaster, and white Super Star.

Leslie's onions

Red Burgermaster, yellow Ailsa Craig and white Super Star sweet onions fill a garden tub trug.

The onion plants were about the size of drinking straws when they arrived, Leslie said. She tucked them into her compost-enriched garden in early May, setting them about 6” apart in wide rows. They got side dressed with North Country Organics’ Pro-Gro 5-3-4 formula at the end of May and again a month later. June and July provided record rainfall, so she didn’t need to irrigate her crop.

Leslie finally announced in mid-August (with much gesticulation and fanfare), “I’ve got 300 HUGE onions!” She brought in an Ailsa Craig to prove it. That onion had a 14-inch circumference and weighed 2 pounds.

Ailsa onion

Our co-worker Kathy LaLiberte grew this Aisla Craig: 17″ circumference, 3 lbs.

I don’t think she’s going back to onion sets next spring. Or ever, for that matter. That’s one of the things I like about gardening—there’s always something new to learn!

-Ann Whitman

Horticulturist, Gardener’s Supply