You don't have to be a botanist to figure out that onions and leeks are related. You can guess that they are kin just by looking at the similarity of their top growth in the garden. These vegetables, along with garlic and shallots, are members of the Allium genus. They all have a distinctive onion-y flavor, although its intensity varies from mild in leeks to the eye-watering pungency of some onions. All are great additions to the home garden, both for their culinary uses as well as their nutritional benefits.
Good to Eat
It's hard to imagine a kitchen without onions! These versatile vegetables are essential to adding flavor to a multitude of dishes, whether it's the mild taste of sweet onions enjoyed raw or the more assertive flavor of yellow onions mellowed by cooking. The mild, sweet flavor of leeks develops as they are cooked in such classic recipes as vichyssoise, the delectable leek and potato soup, and cock-a-leekie, a traditional Scottish soup combining chicken, leeks, barley, and prunes.
And Good for You!
Onions and leeks may not be the first vegetables that spring to mind when we think of nutritional benefits. But onions are a good source of Vitamin C, a number of healthful antioxidants, and dietary fiber -- all for very few calories. Leeks offer similar benefits, and are an excellent source of Vitamins A and K. For the most nutritional benefits from these veggies, let them sit for 5 minutes after slicing or chopping before using.
Tips for Growing Onions
Choose the Right Onion for Your Latitude: Daylength is the signal that tells most onions that it's time to stop growing vegetatively -- putting growth into forming leaves -- and time to start forming a bulb. Long day varieties of onions need exposure to 14 to 16 hours of daylight to bulb up. These onions grow well north of 35 degrees latitude, or approximately above a line drawn through northern North Carolina, Oklahoma, Arizona to central California. These are the onions that are grown for summer harvest in the northern half of the country. They are planted in early spring, putting on vegetative growth until the lengthening days of of early summer trigger bulb formation. Long day onions generally have a pungent flavor and store well.
South of 35 degrees latitude, with its shorter summer daylengths, gardeners need to grow short day onion varieties, ones that form bulbs when the days are 10 to 12 hours long. Short day onions are planted in the fall in the south and grown through the winter for spring harvest or sown in very early spring. Some of the well-known sweet onions are short day varieties. Because of their higher water content, most short day onions do not store well and are best for fresh eating.
Modern plant breeding has produced intermediate day, or day neutral, onion varieties. These varieties aren't as sensitive to daylength and bulb up well in response to 12 to 14 hour days. They grow well across a broad range of the country. Intermediate day onions are usually planted in the spring.
Plant Spring or Fall: Southern and Southwestern gardeners in mild winter areas can plant short day onion seeds in the fall for harvest the following spring or set out short-day transplants in late winter to early spring. In spring, gardeners in all areas can direct-seed onions as soon as the soil can be worked in the spring; start seeds early indoors 10 weeks before planting outside; set out hardened-off homegrown or purchased transplants 4 weeks before the last frost date. Make sure transplants are smaller in diameter than a pencil to lessen the chances of bolting, or going to seed prematurely. Onions can also be started from sets, or small bulbs, set out in early spring.
Mulch the Onion Bed: Onions are shallow-rooted and do best with consistent soil moisture. They also don't compete well with weeds. An organic mulch 3-4 inches deep will help retain soil moisture, keep weeds down, and avoid the damage to onion roots that might occur when weeding.
Harvest When Tops Fall Over: Onions are ready to dig when their tops begin to yellow and fall over. When the tops are browned, carefully dig the onions and let them dry in a well-ventilated spot out of direct sun for a couple of days. If you plan to store onions, let them dry until their tops are completely brown and their outer skins are papery. Then store in a cool, dry, dark location.
Tips for Growing Leeks
Start Seeds Early: Leeks take a long time to mature, so most gardeners will want to either choose purchased leek transplants or start seeds early indoors. Sow seeds inside 8-10 weeks before your last frost date. Whichever route you choose, set out hardened off seedlings in the garden about 2 weeks before the last spring frost date. To grow leeks over the winter in milder climates, start seeds about 8-10 weeks before the fall frost date.
Plant Deep: The edible part of a leek is the white, blanched part of the stalk. To produce leeks with the longest amount of blanched stalk, dig a 12-inch deep, 6-inch wide trench in which to plant the seedlings and gradually fill in the trench as the plants grow. Another method is to poke 8-10 inch deep holes in the soil and drop a leek seedling into each hole. Don't fill in the holes; just water the bed well after planting to settle the soil around the seedlings. The holes will fill in gradually as the season progresses. You can also hill soil up around the stalk to the point just below where the le aves separate.
Keep Plants Fed and Watered: For the thickest stalks, make sure your leeks get consistent moisture and a steady supply of nitrogen throughout their long growing season. Give them a monthly sidedressing with a soluble fertilizer such a fish emulsion.
Q: How do you grow green onions to use fresh?
A: Green or bunching onions, also called scallions, don't form bulbs. Their green tops and blanched below-ground sections are used fresh, both raw and cooked. They may be bulbing onion varieties that are simply harvested when young or they may be different species that never produce bulbs . 'Evergreen White Bunching' is a very hardy, non-bulbing scallion variety that can be planted in early spring for summer harvest or in late summer or early fall to overwinter; protect with mulch in northern areas.
Sow seeds, transplants, or sets for scallions as you would for bulbing onions, but space or thin to only an inch apart. Begin harvesting as soon as the tops are 6-8 inches tall. The more mature the plants, the stronger their flavor. Clumps of the winter hardy varieties can be divided their second summer to produce a new crop.