Alliums-From the Garden to the Kitchen
by Michelle Le Strange, Master Gardener Advisor

Plant alliums like onions, scallions, leeks, and shallots now to savor their flavor later.

ONIONS
In the vegetable garden we grow onions as an annual plant and harvest them before they flower. They are seeded in the fall or early spring, harvested in the summer, and used fresh or stored for winter. In nature onions are biennials; they take 2 years to complete their lifecycle.

Bulb formation: Growing onions to form bulbs takes three ingredients: the right variety, day length and temperature. Generally bulbs begin to form when they receive about 12-16 hours of daylight, which coincides with lengthening of days in spring into summer. Onion varieties are categorized as: short (bulbing starts at 12-13 hours), intermediate (13½ -14 ½ hours), long (14½ - 15 hours) and very long (>16 hours) day types.

An onion plant forms a bulb only after being exposed to its critical day length for several weeks. The bigger the plant when bulbing starts, the bigger the onion bulb. So, establishing a big, vegetative plant with 12-15 leaves is the gardener's goal.

What day length is right for our area? It's been years since grammar school geography, but remember how day length is associated with latitude? Northern gardeners above the 40th parallel (i.e. San Francisco on the west coast and Washington, D.C. on the east coast) can grow long and very long day types. Southern gardeners below the 28th parallel (New Orleans, Miami Beach) grow short day varieties. Gardeners between 28 and 40 (that would be us) grow intermediate day varieties. If we grow short day varieties, bulbs start forming on a very small plant and the onion ends up tiny. If we grow long or very long day varieties, then bulbs just don't form (but they'll make great scallions).

Day neutral varieties are a relatively new development and a great boon to gardeners. They can be grown in almost any latitude and bulb up when the plant has sized up (12-15 leaves).

The temperature factor: Cooler temperatures (below 70°F) retard bulbing even when the required day length is achieved. Warmer temperatures (greater than 75°) hasten the bulbing response. Temperature also affects flowering in onions. Flowering is fine, if you are a seed company producing seed, but for the home gardener the result is a small, tough bulb. This sometimes happens in late spring as our weather shifts between cold and warm spells.

TYPES OF BULB ONIONS
Sweet onions, once called sweet Spanish or Bermuda onions, have high moisture content, moderate sugar, and low pungency. Regionally famous sweet onion varieties like Walla Walla, Vidalia, Maui, and Grano/Granex are the same onion bred for different latitudes. Intermediate day varieties include: Fresno Red, Stockton Red and Yellow, and Pantry Trio - a mix of white, bronze, and red onions. Spring onion is a term applied to sweet onions that are harvested immature.

Storage onions are higher in sulfur content which adds pungency and shelf life. The sugar content is often higher than sweet onions, while the moisture content is less. Over time the sulfur breaks down and the sweetness of the onion intensifies.

Pearl (also called pickling, mini, or summer) onions are small, sweet and not pungent. Italian Cipollini or button onions are flatter and slightly larger than mini onions. They can be white, yellow, or red and taste sweet and creamy when cooked.

SCALLIONS
When looking for scallion seed, use Japanese bunching onions. These are excellent mild scallions. Many presume scallions are immature onions. While young onions look like scallions, they may not match the taste. A good scallion should be mild enough to be enjoyed raw, without the tear jerking pungency of the onion. Still, many sweet onion varieties do satisfy the taste requirement and are easier to find. Intermediate or long day sweet onion types work best like White Lisbon and Sweet Spanish Valencia.

LEEKS
There are summer and winter leeks. Summer varieties are taller with lighter foliage and longer shanks than winter types. Winter leeks offer a richer, meatier taste and texture. Summer varieties can be harvested early for baby leeks or grown to maturity.

SHALLOTS
Shallots are small, onion-like bulbs with a unique flavor. They are more intense than onions, yet less pungent and less sweet. Used in soups and sauces they lend an additional layer of flavor that is more complex than onions, garlic or even leeks.

November 13, 2003