I'd never thought of onions as a dessert food until I baked some Walla Walla onions that had grown more successfully than I'd expected in my garden. They were sweet and crunchy, and I enjoyed them as a cold snack during one of the heat waves this summer.
In California's mild climate, onions can be planted in the fall or winter for harvest in late spring to late summer. Onions can be planted from seed, from sets, or from transplants.
Planting from seed offers the greatest selection, but the best time to plant from seed is September. The seeds are tiny and can be transplanted a couple months later.
Usually, nurseries sell only a few varieties of sets and transplants.
Onion sets are small onions that were planted very close together so that they could not develop into mature onions, then harvested and dried. Often, sets are sold in bags of 100. But since onions are a biennial, they are likely to go to seed, or bolt, when planted from sets. Bolting diverts the plant's resources to seed production, so that the edible part of the onion never fully develops. If you harvest the greens before the tough seed stalk forms, you can still eat green onions (though it's easier to grow perennial varieties if you want a steady crop of green onions).
At a recent presentation by Susan Zaslaw, a UC master gardener, I learned that planting seedlings instead of onion sets was the key to my success this year. I've harvested only a few small onions from the hundreds of sets I've planted over the past couple years, but almost all the seedlings I planted produced medium to huge Walla Walla sweet onions.
Now (October to November) is the best time to plant onion seedlings. Almost every nursery sells transplants in 6-packs. You'll need to separate the tiny plants before planting. Zaslaw demonstrated how to gently separate the onion seedlings: push the bottom of one 6-pack cell to remove the soil block, then swish the soil block in water until the soil is mostly removed. You should then be able to carefully tease the roots apart. If the plants are tiny, you can replant them in spare 6-packs for a few weeks until they're big enough to withstand birds and squirrels in the garden.
Some nurseries also sell “bare-root” onion seedlings – small sprouted bulbs with greens. You don't need to tease them apart, and they are big enough to plant directly into the garden. I planted some of these in December last year with great results.
Many types of onions will grow quite large, so if you want your onions to be small to medium size, plant them closer together. Zaslaw said that one of her favorite onions, Candy, will get 5-6 inches across if they're planted that far apart.
Onions have shallow roots, so they need to be lightly watered a few times a week. Plant them where they can be dry for at least a couple weeks before harvesting.
© 2008 Tanya Kucak