University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article
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CHOOSING ONIONS TO GROW

Dr. Leonard Perry, Extension Professor
University of Vermont 

If you like eating onions and using them in cooking, and have a garden, then you should try growing your own.  They’re easy and don’t take up much room.  By growing your own, you can try many cultivars (cultivated varieties) not available in stores, you’ll know just what chemicals and culture they’ve received, and can save some money. There are different types of onions, so make sure you choose cultivars of the right type for your region, taste, and uses.
           
Onions are divided into types by short-day, long-day, and day neutral.  These refer to the amount of hours of light they need to form their characteristic “bulbs” at the base of the plants in the soil.  Long-day ones require at least 14 hours of light daily to “bulb up”, so are best suited for the North where summer days are longer—generally above the 35th parallel (Tennessee and North Carolina northwards).  If grown in the South, they’ll make nice leaves but little bulbs. 
           
Short-day onions, on the other hand, are best suited for the deep South where they only need 10 to 12 hours of light to form bulbs.  If grown in the North, short-day ones will try to form bulbs too early so won’t reach a good size, having too few leaves.  Then there are day-neutral cultivars that form bulbs regardless of the day length, so can be grown anywhere. 
          
Within the various types by day length, are groupings by color of skin and inner flesh.  Red, or purple, onions have a purplish-red skin and white flesh with some purple coloration which is lost in cooking.  They are mild to sweet, and can get quite large. ‘Redwing’ and ‘Ruby Ring’ are a couple of good long-day cultivars that store well.
           
Yellow onions are the most common type by color, having a brown skin and white flesh.  In Britain and British cookbooks they’re known as brown onions.  They usually are pungent. ‘Copra’ is a good medium-sized, long-day yellow onion that stores better than most. ‘Ailsa Craig Exhibition’ is very large and mild, and grows well in cool weather.  This heirloom has been around since 1887 when it was introduced in Scotland, named for the Marquis of Ailsa at Culzean castle.
           
White onions are just that, white both inside and out.  Often quite strong, they’re the ones often used in Mexican cooking.  Sauteed, they turn a nice brown so are good for onion soup. A mild, day neutral white that is good for slicing or frying into onion rings, is ‘Sierra Blanca’.  This was formerly known as ‘Super Star’—an All-America Selections winner.    Cocktail onions are a very small white type, the one usually pickled in malt vinegar or used in stews, and which may be seen as Silverskin, Pearl, Baby, Boiling, or Button onions. 
           
For all three main color groups there are “fresh” and “storage” cultivars.  Fresh onions, also called spring or summer onions, are best used fresh as they don’t store well (often into fall), and generally are sweet or mild.  Their skins are papery, thin, and light in color. Storage onions, also called fall or winter onions, store well (often into or through winter) and have a strong flavor. They tend to be dark-skinned, with multiple skin layers. 
           
Most onions are somewhat large to really large, including the large and round Spanish onions.  These are mild, produce lots of fruit, but don’t store well.    Bermuda onions, too, are large and mild, with white flesh.  Sometimes sweet onions are called Spanish or Bermuda.  One of the earliest sweet onions, shaped like large flattened globes, are the Maui onions from this Hawaiian island.  They’re often used for onion rings.
           
Large, up to 3 to 4 inches across but really flat like a disc, is the gourmet Italian heirloom cipollini, often found as ‘Borettana Cipollini’.  It is mild with a good flavor, usually roasted whole or on skewers, and is a long day cultivar but best grown in warm climates.

A few other onions have geographic names, including the sweet ‘Walla Walla’ and Vidalia.  The former is named for its origin in Washington state, and is suitable for the north.  The Vidalia refers to a group of short-day cultivars (a main one being ‘Yellow Granex’), grown in that region of Georgia, and which was named the state vegetable of Georgia in 1990. 
           
While most onions are produced at the bottom of the plant in the soil, Egyptian onions are small and produced at the top of the plant instead of flowers. These also are known as tree onions, top-setting onions, or walking onions (as their tops bend down where the bulbs root and grow, thus “walking” through the bed).  A variety of these is grown in Europe as cocktail onions.
           
Another type of onion you may see listed, and that you’re probably familiar with from stores, are the bunching onions.  These also are called scallions, spring onions, green onions, or non-bulbing onions.  These form bulbs no larger, or only slightly larger, than the base of the leaves.  While any onion can be harvested early before the bulbs form for this use, there are cultivars just bred for this use.  The English ‘Guardsman’ is one of the earliest, ‘Evergreen Hardy White’ is quite winter hardy, and the Japanese ‘Nabechan’ has great flavor.
           
Leeks are related to onions, and can perhaps be described as a bunching onion on steroids.  They don’t form bulbs, and it is the thick white base (white from being covered with soil) that you eat—actually the lower parts of the leaf sheaths. ‘King Richard’ is a leek good for earliness and long white stems, while ‘Lancelot’ is more cold tolerant so good for late harvests.
           
Related to onions are the mild-tasting shallots.  They’re like onions on the outside, and garlic on the inside, but aren’t either.  Some use them as a mild form of garlic. Grow them, though, like onions. ‘Picado’, ‘Ambition’, and ‘Saffron’ are some good, long-storing cultivars.
 

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