How to Grow Leeks

Leeks at harvestLeeks are cool-season vegetables that require 120 to 170 days to come to harvest. Leeks are often grown from transplants. Start leeks indoors and set them into the garden in early spring 4 to 6 weeks before the last average frost date when they are about 3 inches tall. In mild winter climates transplant leeks into the garden in autumn or late winter.

Description. The leek is a hardy biennial grown as an annual. Leeks have thick white stalks topped with fanning, deed-green, strap-like leaves. Leeks are mild flavored members of the onion family.

Yield. Plant 12 to 15 leeks per household member.

Site. Grow leeks in full sun. Plant leeks in organically rich well-drained soil. Leeks prefer a soil pH of 6.0 to 6.8. Prepare planting beds a few months in advance adding garden compost and well-aged manure. Leeks are often sown or transplanted into trenches. Prepare trenches 5 inches deep and set transplants at the bottom of the trench. As the plants mature allow the trenches to fill in gradually around the plants.

Planting time. Leeks require 120 to 170 days to come to harvest and grow best where the temperature ranges from 45° to 85°F. Leeks are usually grown from transplants. Sow leek seeds indoors in early spring; set seedlings in the garden 4 to 6 weeks before the last average frost date when they are about 3 inches tall. In mild winter climates transplant leeks into the garden in autumn or late winter. Leeks will tolerate warm temperatures.

Planting and spacing. Sow leek seeds ⅛ inch deep. Thin or transplant leeks to 6 to 9 inches apart. Space rows 12 to 18 inches apart. Leeks are often sown or transplanted into trenches 5 to 6 inches deep. Trenches are gradually filled in over the course of the growing season blanching stems white and mellowing the flavor. Allow watering to naturally collapse the soil around plants filling in the trenches. Leeks can be staggered in double rows; set fanning leaves parallel to the row.

Water and feeding. Keep the soil around leeks just moist; water when the surface becomes just dry. Prepare planting beds with well-aged manure in advance of planting. Add aged compost to planting beds before planting and again at midseason.

Companion plants. Carrots, celery, garlic, onions.

Care. To grow large, white, succulent leeks, blanch the lower part of the stem by hilling soil up around stalks as they develop, or allowing trenches to collapse around the stems. Sandy mulch also can be used to blanch stalks. Hill up around stalks to just below the leaf junction. Do not mulch higher than the leaf junction; this will prevent soil from lodging in leaves and stem. Add straw above plants if the weather nears freezing.

Container growing. Leeks require hilling for best flavor and are not well suited for growing in containers.

Pests. Onion thrips may attack leeks in dry weather. Hose thrips off of plants.

Diseases. Leeks have no serious disease problems.

Harvest. Leeks require 170 days from sowing and 80 days from transplanting to reach harvest. Leeks are ready for harvest when stems reach 1 to 2 inches in diameter and leaves are 6 to 8 inches tall. About midsummer, cut off the top half of leaves to encourage full stalk growth. Lift leeks as you need them but complete the harvest before the first freeze.

Varieties. American Flag (120 days); Arkansas (108 days); Blue Solaize (145 days); Broad London (130 days); Carina (150 days); Gabilian (125 days); King Richard (75 days); Primor (135 days); Titan (120 days); Unique (100 days).

Storing and preserving. Keep leeks in the garden until you are ready to use them. Leeks will keep in the refrigerator for up to one week or in a cold, moist place for two to three months.

Common name. Leek

Botanical name. Allium porrum

Origin. Mediterranean, Egypt