Betty E. M. Jacobs - All the Onions

by Betty Jacobs

Botanical Name:Allium cepa, Cepa Group

Other Names: (Fr.) oignon; (Ger.) Zwibel; (It.) cipolla; (Sp.) cebolla

Life Span: Half-hardy perennial, usually grown as a long-season annual

The right variety is more important for onions than it is for most other vegetables. If you pick a variety adapted to the wrong part of the country (say, trying to grow the sweet Vidalia-type onions in the Northeast), you could end up with nice scallions but no bulbs. The formation of bulbs in different varieties is controlled by how the plants respond to day length. When daylight reaches the right number of hours for that variety, the onion plant stops putting out leaves and starts producing a bulb. The eventual size of the mature bulb depends on how much leaf growth the plant has produced at the time bulb formation starts. If the onion plant hasnt achieved enough top growth (either because it was planted too late or because the variety needs a different day length), the plants wont be able to make bulbs. A cool start encourages the heavy leaf growth necessary for building up good-sized bulbs. Variety alone doesnt ensure good onions; you also need to provide fertile soil, so plants get the nutrients they need to produce good top growth.

Onions are grouped into short-day, long-day, and intermediate varieties. Short-day onions are adapted to growing in southern climates (south of 35 latitude), as they need only 11 or 12 hours of daylight to stimulate bulb formation. They also need mild winters (where temperatures dont go below about 20F), as theyre planted in late fall and grow through the winter. Bulb formation is triggered when days start to get longer in spring. The long winter growing season gives these varieties plenty of time to produce lots of leaves, so they can develop impressively large mature onions by late spring or early summer. The extra-sweet onion grown in Vidalia, Georgia (Granex 33 or Yellow Granex) is a short-day variety.

Gardeners north of 35 latitude need to grow long-day varieties. (The 35 runs approximately through Flagstaff, Albuquerque, Memphis, and Charlotte.) These put out leaves during the long days of northern summers; they dont start making bulbs until the days start getting shorter (14 to 15 hours) as summer wanes.

Intermediate-day varieties, as you might expect, fall somewhere between the other two. They dont need the extra-long days of northern areas, but they need a long growing season. They can be planted from seeds sown outdoors in fall anywhere south or west of Zone 7 (below 35N latitude and up the West Coast through the Pacific Northwest). Intermediate-day varieties can be grown in the North, but only if started from transplants rather than seeds or sets; otherwise, the growing season wont be long enough to form good bulbs.

Did You Know?

The onion is one of the oldest vegetables known. It belongs to a genus of about 280 species of bulbing plants, all having a very distinctive smell. There are hundreds of cultivated varieties, which vary in appearance, pungency, and keeping qualities. They are widely distributed over the Northern Hemisphere, mostly in regions with a temperate climate.

Theres usually a tradeoff between sweetness and storage quality in onion varieties. The onions with the sweetest flavor typically dont store as well as the more pungent types. Many of the largest and sweetest onions are short-day varieties. Many of the best keepers are long-day varieties; while these have a pungent flavor when raw, they lose their bite when cooked and also become milder in storage.

When choosing a variety, read the descriptions youll find in seed catalogs. A catalog should tell you which varieties grow best in what areas, the number of days from planting to maturity, the shape and flavor of the bulb, and whether it is suitable for eating raw, cooking, pickling, and/or storing.

You can start your onions by sowing seeds, by buying started plants, or by planting sets. Starting onions from seeds gives you the widest choice of varieties (so be sure you choose one thats the right day length). It takes 100120 days for most varieties to develop mature bulbs, so plan on starting seeds indoors where the growing season is shorter. You can, of course, use the immature onions as scallions (green onions) sooner. If stored in a cool, dry spot, onion seeds should remain viable for two years.

Buying plants gives you a small choice of varieties, but it enables you to produce an edible crop more quickly. While relatively expensive, its a good choice if you live where the growing season is short and want to produce the largest onions. You can often find flats of seedlings at local garden centers, and now you can order pencil-thick transplants from many standard seed companies. Mail-order transplants are shipped at the appropriate planting time for your area; while they may arrive looking tired from their journey, they recover quickly if planted soon after arrival.

Planting sets gives you even less choice of varieties (unless youve grown your own the previous year; see page 8 for how to do so). But youll get green onions very quickly, and the bulbs will mature three or more weeks before those grown from seeds. Sets are also available by mail order, for less expense than transplants. Theyre a good choice for short-season areas, or where onion diseases have been a problem (sets and transplants are more disease-resistant than are direct-seeded onions).

Onions prefer a loose, crumbly, well-drained, fertile soil with a pH between 6.0 and 7.0. If you have any doubt about whether your soil is well drained, grow onions in raised beds, that is, 4 inches (10 cm) higher than the surrounding soil. Incorporate lots of organic matter to improve drainage and fertility. You can add organic matter at any time, but its best to do this well before planting. That means the fall before planting, where onions will be planted or transplanted in spring; or a month or two before where onions will be planted in spring. Spread a couple of inches (about 5 cm) of compost or well-aged manure over the planting area and turn under with a garden fork or till in. If a soil test shows your soil is acidic, its a good idea to add lime at the same time that you add organic matter; add only enough lime to raise the pH to the ideal range, as too much is worse than too little.

Some Recommended Varieties

Here are a few onion varieties for different areas of the United States. There are many more that are equally good. Check catalog descriptions or ask your local Cooperative Extension Service or garden center. Varieties sold as sets usually do well in most regions; they may be described only as red, white, or yellow sets.

Short-Day Varieties for the North

Plants: Yellow Sweet Spanish (large and mild); Walla Walla Sweet (large, white with yellow skin, one of the sweetest onions for the North); Red Burgermaster (red-and-white flesh). Note: Transplants of intermediate-day varieties also grow well in the North.

Sets: Stuttgarter (yellow, good for storage); Ebenezer

Seeds: EarlyYellow Globe or NewYork Early (early maturing, yellow); Yellow Sweet Spanish (large bulbs); White Sweet Spanish; Copra (one of the best keepers); Southport Red Globe (red skin, pink to white flesh); Mars (relatively early, red)