Like their cousins onions and garlic, leeks are members of the Allium family, though they are harder to find, giving them a bit of a rare and special reputation. Lucky for us gardeners, they’re actually quite easy to grow, so their mild, delicious, sweetness and helpful vitamins and antioxidants can be yours directly from your backyard!
Leeks are essentially a bulb-less onion. They are grown for their stout, fountain-shaped stalks that feature a sweet, mild, onion-like flavor. Most varieties have handsome, blue-green leaves.
Leeks have two distinct parts, the top darker greenish-blue leaves, and the lower white to pale green stalk. The top greens are great to save for veggie stock, but are usually too tough to eat, so we concentrate on eating the tender stalk, which stays pale by blanching. During the growth cycle, we blanch the stems by mounding soil around them as they grow. Blanching causes stalks to grow longer, taste more tender and milder, and turn white.
Leeks are a long-season crop, generally planted in early spring for harvest in fall or early winter. Some varieties with shorter days to maturity can be harvested as early as midsummer; others are bred for resistance to freezing temperatures. If mulched heavily in fall, they can be harvested right through winter in areas where temperatures remain above 10°F.
Planting and Aftercare:
Leeks are quite easy to start from seeds! Start seeds indoors in your favorite seed starting mix about 12 weeks before your last frost date. Plant three seeds per cell/pot and thin to the strongest seedling when 2” tall.
About a month before your last spring frost date, work compost into your soil and dig a 4-6” trench. Plant seedlings in the bottom of the trench. Gradually fill in the trench as the seedlings grow by hoeing soil into it. Continue mounding soil around plants until midsummer. Water regularly and keep the bed free of weeds for vigorous top growth.
Leeks can also be purchased as starts, usually shipped to you as bare rooted bundles in early spring. When working with these, you’ll want to plant when your soil temperature has reached 50 degrees. This is typically four weeks before your last frost. Poke a hole in the ground about 2 inches deep with your finger. Taking care not to damage the roots, place the start into the hole to a depth of about ½ inch and lightly press the dirt around the plant to secure it.
Keep your newly planted leeks evenly moist until well established. Topdress monthly with compost, and harvest anytime after the stalks become thick. In milder climates (about zone 6 and above), before your first hard frost in fall, mulch plants with 1’ of straw to keep soil from freezing.
Harvest plants as needed through winter. In areas with colder winters, dig leeks in late fall. They freeze and dry nicely for use throughout winter, and you can also store them in moist sand in a cool place for up to 8 weeks.
Tips for Success:
Allium seeds have a short shelf life. Be aware of the sell-by date of the seeds you are interested in, and only buy seeds that are dated for the current season you are in, and plan on using or sharing your leftovers with friends within that season.
Leeks are cold tolerant, and you can plant as early as late winter with the aid of a floating row cover to protect your seedlings from frost.
Unblanched leeks will have short stalks with tough flesh. If your soil is heavy clay and difficult to trench without risking the leeks sitting in waterlogged soil, you can try slipping cylindrical, ceramic drain tiles or 8-10” sections of 4” wide PVC piping around each plant, and mound soil up. These pieces of piping essentially act as individual raised beds for each plant.
Pests to Watch For:
Onion maggots can tunnel into leeks, leaving visible holes and making them susceptible to disease. Cut off and destroy any infested areas; portions without tunnels are still edible. This pest thrives in wet soils, so make sure that your beds are made up of well-drained soil.
Growing Zone and Special Conditions:
Leeks are annuals and easy to grow in all areas of the United States. Cooler climates will do well to keep their leek plants in full sun, and warmer climates with hot summers might benefit from tucking their plants in the shade of other crops to protect them from sweltering summer sun. Leeks are essentially a full sun crop, but will tolerate and may benefit from some partial shade.
As members of the Allium family, leeks are susceptible to the same pests that can trouble onions and garlic. Keep this in mind when you are planning your crop rotations for following years.
Planting leeks near carrots can help repel carrot rust flies, which may or may not be in your area. Leeks are good companion plants for broccoli, cabbage, and celery.