Leeks

Growing Conditions

Leeks are cold-hardy alliums that prefer cool temperatures but tolerate heat better than onions. They grow through summer and are harvested in fall and winter — late-season varieties survive hard frosts and can be left in the ground until needed. Full sun and fertile, well-draining soil produce the best results.

Cold climates: Start indoors 10–12 weeks before last frost. Transplant after last frost, once soil has warmed slightly. Harvest from September through December or later with mulch protection.

Warm climates: Start in late summer for fall and winter harvest. Leeks are more adaptable to mild-winter climates than most cool-season crops.

Sowing & Planting

Start seeds indoors ¼ inch deep in trays or cells. Transplant when seedlings are pencil-thin, 8–10 weeks old. Trim roots to 1 inch and tops to 3 inches before planting to reduce transplant shock. Plant in furrows 6 inches deep, dropping transplants in and back-filling only partway — the trench method produces long, well-blanched shafts. Space 6 inches apart.

As plants grow, gradually hill soil up around the stems to blanch (whiten) the shaft. More blanching produces more of the tender white portion most recipes use.

Care & Maintenance

Water consistently — leeks are heavy feeders and need regular moisture throughout their long season. Side-dress with compost or balanced fertilizer monthly. Keep soil hilled around stems throughout the growing season.

Common Problems

Leek rust — bright orange pustules on leaves — is common in wet seasons. Largely cosmetic; doesn’t affect the edible portion. Choose resistant varieties. Onion thrips cause silvery streaking; control with insecticidal soap. Bolting can occur if transplants experience a hard cold snap early in the season — use cold-hardy varieties and don’t rush transplanting.

Harvest

Harvest leeks at any size once the shaft reaches ½ inch or more in diameter. Loosen soil with a fork and pull. Leeks left in the ground through frost develop sweeter flavor. Late-season varieties handle temperatures down to 10°F–15°F with mulch protection. Harvested leeks keep 1–2 weeks refrigerated; store unwashed with roots attached.

Varieties

Early varieties (King Richard) mature faster but are less cold-hardy — suited to spring planting and fall harvest. Late/winter varieties (Bandit, Bleu de Solaize) are cold-hardy and can be left in the ground through winter. For most home gardens, a late variety provides the longest harvest window.