Leeks are a cool-season member of the onion family, grown for their thick, mild-flavored white shanks rather than a rounded bulb. Home gardeners in the US value them for their sweet, delicate onion taste and for their long harvest window, which can stretch from late summer well into winter in many regions. They are more cold-hardy and less pungent than onions, making them a rewarding crop for cooks who want a steady supply of alliums.

When and how to plant

Leeks have a long growing season, often 100 to 150 days from seed, so most gardeners start them indoors 8 to 12 weeks before the last spring frost and set transplants out once the soil can be worked. Choose a spot in full sun with loose, fertile, well-drained soil that holds steady moisture. Space plants about 6 inches apart in rows 12 to 18 inches apart, and set transplants deep in a shallow trench or a dibbled hole 6 inches deep to encourage a long, blanched white shank. In mild-winter areas you can also sow in late summer for an overwintered spring crop, since leeks are biennials that tolerate cold well.

Care

Keep the soil evenly moist throughout the season, as leeks are shallow-rooted and grow slowly, and a layer of mulch helps conserve water and suppress weeds. Because it is a long-season, heavy-feeding crop, work plenty of compost or aged organic matter into the bed before planting and side-dress with more organic matter partway through the season to sustain steady growth. To lengthen and whiten the tender edible shank, gradually hill loose soil or mulch around the stems as they grow, being careful not to bury the point where the leaves fan out. Weed regularly and shallowly to avoid disturbing the roots, and keep the crop watered right up until harvest.

Common problems

Common pests include onion thrips, which scar the leaves, and the leek moth and onion maggot, whose larvae tunnel into the plant. Diseases to watch for are rust, which shows as orange spots on the leaves, along with downy mildew, purple blotch, and the soilborne white rot. Rotate alliums to a new part of the garden each year, space plants for good airflow, remove and destroy affected leaves, and use floating row covers to keep egg-laying insects off young plants.

Harvest

Harvest leeks anytime once the shanks reach about 1 inch or more in diameter, loosening the soil with a fork before pulling so the roots do not snap. They are very cold-hardy and can stay in the ground into winter under a thick mulch, letting you dig them as needed rather than storing them all at once. Trim the roots and tops, then keep harvested leeks in the refrigerator, where they hold well for several weeks.

Popular Leeks varieties to grow

Leek varieties are usually chosen by shank length, cold hardiness, and whether they are best for summer, fall, or overwinter harvest. For home gardeners, the most useful distinction is early versus hardy late-season types.

Variety notes are general guidance for US home gardens; local performance varies by climate and season. Availability differs by seed supplier.

Growing Leeks in containers

Leeks grow well in deep pots and are a good container crop for cool seasons. Use a container at least 12 inches deep with drainage, spacing plants 4 to 6 inches apart in fertile potting mix. Keep the soil consistently moist, feed periodically with a nitrogen-containing fertilizer, and mound mix around stems as they lengthen to produce longer white shanks.

Watering & feeding Leeks

Provide about 1 inch of water per week, increasing toward 1.5 inches in heat, drought, or sandy soil. Leeks have average water needs, but dry spells can slow growth and make stems tough. Water deeply at the base when the top inch of soil begins to dry, with more frequent checks for containers. Mulch helps retain moisture, and morning watering keeps leaves from staying wet overnight. Wilting and thin, tough plants suggest drought stress, while yellowing in constantly wet ground may indicate excess water.

Leeks are moderate feeders and benefit from compost worked into well-drained soil before planting. Nitrogen supports steady leafy growth, while balanced levels of phosphorus and potassium support roots and overall vigor. Add compost before planting, then side-dress lightly with nitrogen or a balanced vegetable fertilizer after plants are established and again during midsummer if growth is slow. Feed lightly and consistently rather than heavily all at once. Do not overuse nitrogen late in the season, especially if plants are already growing well. Keep soil moisture even while hilling soil around the stems for blanching. Water the soil after hilling to settle it without washing soil into the leaf folds.

Saving Leeks seeds

Save seed from open-pollinated or heirloom leeks, not F1 hybrids, and isolate varieties because insects can cross-pollinate them. Leeks are biennial, so retain healthy, true-to-type plants through winter and let their second-year round flower heads dry until black seeds are visible. Cut mature heads before seed drops, dry them fully, rub out the seeds, and remove chaff. Store cool, dark, and dry, and use leek seed within about 1 to 2 years for best germination.

Leeks companion plants

Grow leeks with carrots, celery, lettuce, and strawberries. Their narrow leaves use little horizontal space, carrots and leeks are a classic mixed planting for pest diversification, and lettuce can be harvested before leeks enlarge. Avoid peas and beans immediately nearby, because alliums can inhibit legumes and the two crops are not an especially compatible use of bed space.

Frequently asked questions about Leeks

General guidance for US home gardens. Reference figures are typical values; your exact timing depends on your local frost dates and variety. Page updated Aug 4, 2026.