Fall and winter – when most of the vegetable garden is slumbering – is a great time to get a jump on next year’s onion, scallion, and shallot crop. Most members of the onion tribe (known botanically as Allium) are hardy perennials and biennials that tolerate winters in most areas of the U.S. Garlic (as discussed elsewhere on this site) is one well-known and often-grown example – but winter onions and shallots are also ideal winter-growing crops for USDA Hardiness Zones 6 through 9 (in zones 4 and 5 they need winter protection).
Common Garden Onions
Early-ripening, short-day onions (Allium cepa), requiring only 10-hour days for bulb formation, have long been a staple crop in mild-climate regions of the U.S, where they’re planted in late fall or winter and harvested in early spring. In areas with shorter growing seasons, gardeners have had to settle for spring-planted onions that form bulbs during the long days of summer.
Fall-planted, spring-harvested onions are now a thing in cold-winter climates, thanks to the recent development of so-called “overwintering (OW) onions”. In addition to possessing exceptional cold-hardiness, OW varieties do not flower (or “bolt”) after prolonged chilling, as other onions do. Consequently, they put all of their energy in spring growth, building fat succulent bulbs, rather than in forming flower stalks that compromise the bulbs’ size, flavor, and texture.
Start OW onions in fall from sets or in late summer from seed (thinned seedlings taste great in fall salads and stir-fries!). To produce the largest, earliest onions, give them a winter mulch and overhead protection (such as a cold-frame or “mini-tunnel”) in USDA zones 6 and below.
Most OW cultivars are intermediate-day onions, which will bulk up in early spring as days become longer than nights. Among the best are:
‘Bridger’, an extra-hardy variety with large, yellow, pumpkin-shaped onions that plump up nicely in early spring even in unprotected soil in USDA zones 6 to 9 (in colder zones, protection is usually required to produce large onions).
‘Tough Ball’, a long-storing, medium-sized, globular yellow onion with leathery outer skin.
‘Electric’, one of the few red overwintering onions, with crisp maroon skin and pink-tinged flesh.
Welsh or Bunching Onion
Sown in early summer, this delightful, long-lived perennial yields a bountiful harvest of zingy scallions and greens from early fall until the ground freezes. Even better, the slender bulbs of Welsh or bunching onion (Allium fistulosum) resume growth in spring and multiply throughout the growing season to provide a steady dig-and-come-again crop, year after year. Suitable for display in perennial gardens as well as veggie gardens, Welsh onion produces showy spheres of fuzzy white flowers atop inflated, hollow-stemmed, 2-foot-tall stalks in early summer. Despite its common name, it originated in East Asia, where it’s long been a favorite (but apparently the Welsh enjoy it too).
Numerous varieties and hybrids of Welsh onion – selected for flavor, color, hardiness, and other characteristics – are offered by seed merchants. They include:
‘Nabechan’, noted for its thick, richly-flavored scallions that are ideal for blanching. (You can mound soil around the plants several weeks before harvest to produce pale, tender stems.)
‘Evergreen Hardy White’, lives up to its name by toughing out winters into USDA Zone 3, if given a winter mulch.
‘Guardsman’, is a hybrid Allium cepa that yields tasty bulbous scallions in fall and spring from a summer sowing.
‘Deep Purple’, is a burgundy-hued counterpart to ‘Guardsman’.
Egyptian Walking Onion
This bizarre variety of common garden onion sends up tall stalks in summer topped with clusters of small shallot-like bulbs that develop roots in midair. The fattening bulbs eventually cause the stems to topple to the ground – a sign that they’re ready for harvest. Unharvested Egyptian walking onion (Allium cepa var. viviparum) bulbs typically root into the soil while still on the stem tips (hence the name “walking onion”). They can be left in the garden to provide next year’s crop, or gathered for the table as long as the soil remains unfrozen.
Use harvested bulbs for pickling or in soups and stews, reserving a few for replanting in fall, if necessary. (Bulbs for planting can also be purchased from specialty seed companies.) The bulbs keep well for most of the winter in a cool, dry, dark location. Self-planted and replanted bulbs sprout in early spring, pushing up plump chive-like leaves that are delicious in salads, baked dishes, and stir-fries.
Shallots produce prolific clusters of small, firm bulbs – marking them as members of the onion subgroup know as multipliers (Allium cepa var. aggregatum). Although their seed can be sown in spring for a late-summer crop, shallots are often raised from sets planted in fall, which are ready for harvest in early summer. Almost all shallot varieties are “long-day” plants, requiring 14-hour (or longer) days to form bulbs. Consequently, they perform well only in higher latitudes (at least 40 degrees from the equator).
As with most bulbing onions, they’re best dug after their leaves start to yellow and flop. Be sure to set aside a few bulbs to replant in fall for next year’s harvest. Winter mulch is advisable in zones 4 through 6.
The subtle garlicky oniony flavor of shallots works well in stews, soups, casseroles, stuffings, and numerous other dishes. Bulbs keep for many months in cool storage, and even longer if pickled in vinegar.
Starting Winter Onions
Sow culinary Allium seed in summer in full sun and fertile, friable garden soil, and you’ll be harvesting succulent onions, scallions, and shallots long after you put the rest of the vegetable garden to bed (and long before you plant most of next year’s tender veggies). Or you can purchase them as young bulbs (known as “sets”) and plant them in early fall.
Plant onions from sets with the bulb tips just below soil level. Whatever the winter-hardy alliums you choose for your vegetable garden, you’ll want to give them an inch or two of Fafard® Premium Natural & Organic Compost, either as a mulch or forked in before planting. You’ll love the results! In USDA Zones 4 and 5, plants usually benefit from a protective winter mulch of straw, pine needles, or oak leaves.