Each year a substantial portion of our vegetable and small fruits garden is devoted to the genus Allium, perhaps a third of the total bed space. Garlic and shallot cloves, planted in October, spend the winter under a blanket of snow. In early May, as soon as the risk of hard freeze is past, in go transplants of onions and leeks. At one end of the small herb bed a clump of chives sends up its slender leaves in May and, to the delight of bumblebees and butterflies, its rounded tufts of lavender flowers in mid-June.
Some vegetables, like cucumbers, tomatoes, tomatillos, and summer squash, we grow for the immediate joys of accomplishment and rich flavor. But the garden space devoted to onions, leeks, shallots, and garlic is an investment in the future. Stored in mesh bags hanging from the basement rafters, one or more of these essential alliums will be a part of nearly every evening meal from the day they are harvested until the supply is exhausted. Garlic and shallots are harvested in August, onions between late August and early September, leeks as we need them up to the first hard freeze.
We grow Copra onions, dark yellow and medium-sized, 3-to 4-inches round, pungent but sweet, the best variety for cooking. We grow them from transplants ordered to arrive at least four weeks before the last frost date, plants grown in fields of Georgia or Texas, giving them a several-week jump on our season and on weeds, advantages that promote production of large bulbs. Copra is one of the highest in sugar content of all onion varieties, becoming milder in flavor with time in storage. It will keep for a year, the last bulb brought up from the basement as rock hard as the first.
For immediate use, we grow Walla Walla Sweets, a French heirloom variety brought to Washington State by a Corsican immigrant in the early 19th century and described in contemporary seed catalogs as a “juicy, sweet, regional favorite”. In Washington the seeds are sown in August and the young plants overwinter in the ground; bulbs form the following spring and are harvested in early summer. In Maine, we have to settle for transplants that don’t grow as big a bulb, but are still sweeter than many other spring-planted varieties.
You can try growing other varieties if you like, but make sure that they are long-day onions like Copra and Walla Walla Sweets, varieties that can be planted in April and grow leaves until June when 14-hour days trigger a change from growth to storage, leaves to bulbs.
We plant onion transplants as early as possible, four to six weeks before the date of the last expected spring frost. Onions can take cool soil and light frosts and require protection only from hard freezes. If we see a hard freeze coming after planting, we water the plants thoroughly and cover them with a straw mulch.
For producing the largest bulbs, onions require a deep, humus-rich soil, perfect drainage, a pH near 7.0, persistent weed control, and regular watering. Onions survive periods of drought by using water stored in the developing bulbs, thereby reducing bulb growth, and weeds are serious competitors for available water. Thus irrigation during dry periods is essential for production of large bulbs. I use the knuckle rule to determine when to water during the season, sticking a finger in the ground up to the first knuckle. If I can feel moisture, then the onions are wet enough.
Mulching helps reduce competition for water from weeds while maintaining uniform soil moisture levels for a longer period. We use shredded leaves as mulch for all the allium beds. Weeds that manage to grow through the mulch are pulled by hand; a hoe will nick the young bulbs. This business of keeping onions weed-free is a challenge that I readily accept – it is an excuse to be in the garden. We select our onion bed early in the season, a bed in full sun with excellent drainage, and keep it free of weeds, pulling them by hand or hoeing them out as they appear. Once planted, hand-weeding the onion bed is the first and last chore of every gardening day, never letting a weed grow beyond the seedling stage.
Available sunlight is another critical factor. In summers with too many overcast days, onion bulb size is likely to be smaller. Pick your sunniest beds to grow all of the alliums, at the same time remembering to rotate vegetable crops to prevent diseases. Onions and other alliums should never be grown where a member of the allium genus was grown the previous year.
Think of leeks as the milder-tasting, more frost-tolerant member of the onion family. Many varieties, such as ‘King Richard’, have large, dark blue-green leaves, an attractive ornamental feature in the edible landscape. Their upright, non-spreading habit makes leeks ideal plants for intercropping with other vegetables.
Cooked or uncooked, leeks are as versatile in the kitchen as onions. They can be used in soups, quiches, stews, casseroles, and salads, often as an onion substitute when a more subtle flavor is desired. The can also be prepared alone, as a fall or early winter fresh vegetable.
Leeks are long-season plants that are best planted in the garden as seedlings that you grow yourself or purchase from commercial growers. I’ve been successful with both approaches, but prefer to buy transplants, ordering them at the same time that I order my onion transplants. These starter plants are much larger than any I could produce under the lights at home.
Leeks grow best in full sun. They need a garden soil with high fertility, plenty of organic matter, and a soil pH between 6.2 and 6.8. The soil must hold plenty of moisture during the growing season but be well-drained in winter to prevent ice encasement of plants left in the soil.
We plant our leeks in the garden eight to ten weeks before last frost, setting the plants into dibbled holes that are four to eight inches deep, leaving only a few inches of leaf above the soil. We leave about five inches between rows. The holes gradually fill with soil washed in by rain or irrigation. This method of planting, recommended by leek growers with far more experience than we have, is preferred over covering the plants all at once, which can result in rotting. As the leeks grow, continue to hill or mound soil around them periodically to blanch the stems. During summer, mulch the soil around the plants with straw or shredded leaves. This will hold moisture in the soil, prevent weed growth, and blanch more of each plant’s stem.
Leek varieties differ in their cold tolerance with some varieties better suited for summer harvest and others for fall and early winter harvest. The early variety King Richard, for example, did well for us in last year’s summer garden and we are growing it again this year, along with Lancelot, a later maturing variety recommended for fall and early winter harvest.
With both onions and leeks available at the grocers throughout the year, why would a gardener want to grow his own? I cannot make the case that home-grown onions and leeks taste better than their grocery store counterparts. And I’m sure that my home grown onions and leeks cost me more than the store-bought kind. For me, and particularly with onions, the reward lies in producing a crop that will satisfy the kitchen’s needs through the winter. In other words, the reward is in the pleasure of growing them. Each time I bring up a handful of Copra onions from the basement, I feel connected to the garden by an act that reminds me of last season’s success and, for a brief moment, allows me to dream of the season to come.