Growing Great Onions

Friday, January 23rd, 2015 by Jenny Watts
    • Prune fruit trees, grapes, berries, and ornamental trees this month. Take in a pruning class and sharpen your shears before you start.
    • Spray fruit trees with a dormant oil spray. Spray from the bottom up, including the undersides of limbs and the ground around the tree, to prevent early spring insect infestations.
    • Tree collards are delicious winter vegetables. Set out plants now.
    • Start seeds of perennial flowers like columbine, coreopsis and echinacea.
    • FREE Fruit Tree Pruning Class this Sunday, January 25, from 10 AM to 2 PM at Sanhedrin Nursery, 1094 Locust St., Willits.

Growing Great Onions

Onions seem like they would be one of the easiest vegetables to grow, but raising good onions can be more complicated that it first appears. As vegetables they are interesting plants to grow because they are very dependent upon day length and temperature to form bulbs.

Onions are typically seeded in fall through early spring, harvested in early summer and used fresh or stored for winter. But as many experienced gardeners know, the crop is not always successful, and many times the bulbs produce flower heads, which is known as “bolting”.

To grow onions successfully, you must know a little about them. Onions are biennials, which means that they grow one year and makes flowers and seeds the second year. The first year the onion plant begins its growth by putting out its green top leaves in cool weather. It stores energy in those leaves until the weather gets warmer and the days get longer. Then it begins storing energy in the bulb underground. When the bulb is mature, the leaves turn yellow and die and the onion is ready to harvest.

Given a certain set of environmental conditions, onions can be tricked into believing they have gone through two growing cycles during their first year. Instead of finishing with a well-cured bulb, ready to harvest, a seed stalk can develop prematurely, causing onions to be unmarketable.

Fall seeded crops are susceptible to bolting the following spring if warm fall temperatures, allowing excessive growth, are followed by low winter temperatures and slowed growth. The most successful onions may come from transplants set out in early spring.

Occasionally other factors, such as damage by cultivation or excessive stress, may cause bolting. That’s why only a few plants may bolt in an entire plot. Should this occur, the onion will still be perfectly edible; however, as the seed-stem gets bigger, the ring inside the onion will become pithy and inedible. If left to maturity, this ring will rot quickly and cause the entire onion to rot as well. It’s best to eat the onion as soon as you see the seed-stem. Don’t bend or break the top; the leaf is hollow, and breaking it will allow water to go right into the center of the onion and cause it to rot.

Onion sets (the small dry bulbs) have a bad habit of bolting and producing a flower stem. It is actually better to plant first-year seedling onions. These come two ways: as nursery-grown seedlings in small pots, and in bunches of larger seedlings that have been grown in fields and dug-up. The latter are available now in a limited number of varieties, and the former will be available soon with other spring vegetable starts.

Onions are characterized by day length: “long-day” onion varieties will quit forming tops and begin to form bulbs when the day length reaches 14 to 16 hours while “short-day” onions will start making bulbs much earlier in the year when there are only 10 to 12 hours of daylight. As a general rule, “long-day” onions do better in north of 36 degrees latitude while “short-day” onions do better south of that line. Willits and Ukiah are at about 39 degrees.

Our long summer days make the intermediate to long-day onions good for our climate and latitude. These include Red Zeppelin, Walla Walla, and Copra, Ruby, Candy, the Southport Globe onions, and Yellow and White Sweet Spanish.

For keeping qualities, the strong-flavored, yellow ones, like Copra, Yellow Spanish and Yellow Globe are the best. The milder onions don’t develop the really firm outer skin needed for long storage.

Onions aren’t bothered by frost, so early spring is the best time to get them planted. Then they have plenty of time to store up energy in the leaves before bulb-making time. The more green growth, the bigger the bulbs will be. So get started with onions, now.