July 14, 1998

Onions can be one of the more vexing vegetables to grow in the Maritime Northwest. The seed germinates slowly, and won't push through crusted soils. As seedlings the plants are senstive to temperature, and often do poorly in our wet, cool springs. And as if that isn't enough, the plants themselves are just not that vigorous if grown in less-than-ideal soils! Many Northwest gardeners have allocated a full summer's worth of garden space to growing onions, only to harvest what amount to pungent golf balls.

In order to get around the well-advertised difficulties starting onion seed, many gardeners grow onions from sets as a matter of course. Set-grown onions have their own problems, though, including inferior eating quality, a high percentage that bolt instead of bulb, and a relatively short storage life.

I'd like to suggest an alternative to you, my fellow Northwesterners. Try growing overwintered onions! These types, hardy to below 0F, offer several advantages for the Pacific Northwest gardener.

Overwintered onions are in the ground a lot longer than their summer counterparts - roughly 300 days. Because of this, they have more time to develop a vigorous root system, which means they grow more strongly on heavy soils. In addition, overwintering types do most of their growing during spring, when soil moisture is plentiful. They mature and dry down in early summer when the days are at their longest. All these factors add up getting larger onions with less effort.

Some overwintered onions beginning to form bulbs.

Since these onions are ready to harvest between June and early July, the (usually) dry weather we receive then is much more conducive to good curing. The newer varieties of overwintering onions will easily keep well into fall if cured properly. So, if you also grow leeks, you can have alliums available year-round without too much effort.

Now I don't want to give the impression that these are the miracle byproduct of modern allium science. One shortcoming they share with other onions is the less than ideal vigor of the seed. Given that you have to sow these during the heat of August, this definitely is a concern. I do have a couple of tips that should help with growing any onions from seed. First, make sure you are buying quality seed from a reputable vendor. Don't buy them off a seed rack; instead, mail order them from a quality company, and then store them under good conditions. Second, when you sow them don't cover them back up with dirt. Instead, use sifted compost, seed starting mix, or fine-grade vermiculite, all of which hold water and will not crust over.

Another potential problem for most overwintered alliums (including onions, scallions, and garlic) is the constant rainfall and saturated soil we experience most winters. It can be wise to grow any alliums in raised beds, to improve the drainage a bit. If you can do it, getting some sort of cover over your overwintered onions will result in less winter damage, which will translate into stronger, earlier growth the following spring. I have had good results growing these onions in a couple of fairly dense rows under my PVC hoophouse. In February I dig them carefully, and transplant them out to their correct spacing (3-4 inches apart) in an uncovered garden bed. I side-dress them at this point with blood meal. Then in mid-April, and again in mid-May, I side-dress them again with a complete organic fertilizer.

As of now, Territorial Seed Company seems to be the only good source for overwintered onion varieties. Many other companies do at least sell Walla Walla, the justifiably famous onion from across the mountains. Walla Wallas do not keep worth a darn, and they don't dry down until July. However they taste wonderful, and the late maturity means they are more forgiving of a late planting date the previous fall. I'd say if you are not confident in your gardening skills, try Walla Wallas the first year.


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This page was last updated November 18, 2013