Leek Growing Guide

Leeks are a non-bulbing, cool season onion-relative with leaves that grow in a tight cluster up to several feet high. They are milder tasting than onions, and have a distinctive flavor that adds zest to soups and stews, and enhances stuffings, gratins, and casseroles. They also add a nice flavor when sauteed with other vegetables.

The white portion of the stem is used in cooking, just as with scallions.

When to Sow Sun/Part Shade Seed Spacing Row Spacing Planting Depth Spacing After Thinning Days to Germinate Days to Maturity
8-10 weeks before last frost Full Sun or Part shade 1 inch 10-12 inches ½ inch 6 inches 5-7 120

Soil and Fertilizing
It's best to have your soil tested before planting, to find out what nutrients and pH levels are needed for your plants. For a thorough soil test, visit an Agricultural Experiment Station in your area (scientific research center) or consult your local county extension agent (also known as a Land Grant University).

Leeks prefer a well-drained soil, rich in organic matter, with a slightly acidic pH of 6.0-6.8. Composting can help prepare the soil for leek cultivation. They require a minimum soil temperature of at least 40° F to mature.

Planting
Leeks can be direct-seeded or transplanted. Start your seeds indoors about 8-10 weeks before the last frost. Then transplant the seedlings into the garden two weeks before last frost, 4-6" apart, when the plants are at least 8" tall and as thick as a pencil. Leeks thrive in raised beds.

Plant them in an area where onions have not been grown in the past three years, as they can pick up pests and diseases onions leave behind.

To prepare the seedling for transplanting, cut off half the green leafy top and don't bend the roots. Afterward, mulch the plants to conserve soil moisture and deter weeds. Hill the soil or mulch around the stems to blanch them. The stems are blanched (kept white and edible) when they are under the soil away from the sun; if exposed to the sun, they'll turn green and inedible.

Watering
Leeks are shallow rooted, so you must keep them well-watered and protected from weeds. Mulch will help keep moisture in and weeds out. One inch of water per week should be sufficient.

Harvesting / Storage
Leeks are mature when the stalks are about 1" in diameter. This takes about 120 days from seed.

Loosen the soil before pulling up the leeks so they don't break off. You can let the hardy long-season leeks remain in the garden until just before the ground freezes or through the winter in warmer climates.

Harvested leeks can stay wrapped in plastic in the refrigerator for up to 2 weeks; cut off all but a few inches of the green tops so they are easy to store.

For additional information specific to your growing area, please consult your local county extension office.

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