We plant onions in spring because they need cool soil temperatures to germinate and a long growing season to mature. Choose the variety carefully to ensure success. Onions are categorized as long day, short day, or day neutral. Not all day-neutral onions will form bulbs here.
As I wrote in my Feb. 3 column, many factors influence plant growth. Day length is a critical factor for onions. Onions, which we may plant in March, make top growth until lengthening days trigger bulb formation.
Days are longer at northern latitudes, where there are 14 to 16 hours of daylight during late June and July. The dividing line between “long” and “short” days in the onion world is generally accepted to be 36 degrees latitude. This is roughly the Kansas/Oklahoma border. Here in our area, we are at approximately 35 degrees latitude and so must grow the short-day varieties.
Sandy loam is ideal for onions, so this is another crop best grown in raised beds. Onion seed germinates when the soil temperature is between 50 and 75 degrees. It is more common to grow onions from “sets”—that is, bunches of seedlings—than from seed. Plant sets about 7 inches apart in rows one to two feet apart.
Whether grown from seed or set, onions take months to mature. They are ready to harvest when about half of the tops have fallen over. Push down the rest. Wait a week before digging the bulb. Onions can then be stored for several months in a cool, dry location.
Bunching onions are grown from seed in spring for harvest in late spring and early summer. They may be sown again in late summer for autumn harvest. Leeks want cooler temperatures to germinate and mature later. One can plan to harvest several varieties over an extended period from late summer through fall.
I just may try to grow leeks this year. They are always expensive, and now I know why.
Onions are native to the temperate areas of the northern hemisphere. No doubt folks have been eating them since caveman days. Apparently they were popular in ancient Egypt where along with being eaten, they played a role in mummy making.
Onions, leeks and garlic are mentioned fondly in Numbers 11:5. In ancient India, onions were used medicinally as an anti-inflammatory agent and as a diuretic.
Among some groups in Asia, onions and garlic are not eaten. I have heard two myths about the origin of this custom. Both involve demons roaming about creating onions and garlic, making them devil’s food.
Onions certainly add a lot of flavor to food, but do they have any nutritional value? They are a good source of vitamins C, B6, and folate as well as manganese and fiber. Being 89% water, 9% carbohydrate, and 1.7% fiber, onions are a low-calorie, low-sodium vegetable. Intolerance to raw onion is not uncommon, leaving afflicted individuals with indigestion after consuming this treat.
Never feed onions or garlic to dogs and cats as it may lead to a life-threatening condition called hemolytic anemia. Our pets do not have the digestive enzymes needed to process some substances in onions and garlic.
Ann Bartlett is a master gardener who grew up in agricultural California. She, ahem, knows her onions.