Leek

Plant Overview

Leek (Allium ampeloprasum var. porrum) is listed in the Amaryllidaceae family and categorized as a vegetable with a biennial commonly grown as an annual crop life cycle. This profile summarizes growing information for hardiness, light, soil, water, seed starting, maturity, and other available cultivation details. Difficulty is listed as Moderate.

Plant ID

PLT-0036

Family

Amaryllidaceae

Plant type

Vegetable

Life cycle

Biennial commonly grown as an annual crop

Growth habit

Upright cool-season biennial commonly grown as an annual, producing broad flat leaves and a thickened white leaf sheath rather than a true bulb

Mature height

Commonly about 18-36 inches tall, depending on cultivar and growing conditions

Mature spread

Commonly about 6-12 inches wide

Difficulty

Moderate

Growing Conditions

Leek is listed for full sun conditions. Water needs are listed as moderate; keep soil consistently moist during active growth while avoiding prolonged waterlogging. The database soil reference is Deep, fertile, well-drained loam rich in organic matter and capable of holding steady moisture. The listed soil pH range is 6.0-7.0, and the listed hardiness range is 2-9 as an annual crop.

Hardiness zones

2-9 as an annual crop

Sunlight

Full sun

Soil

Deep, fertile, well-drained loam rich in organic matter and capable of holding steady moisture

Soil pH

6.0-7.0

Water needs

Moderate; keep soil consistently moist during active growth while avoiding prolonged waterlogging

Plant spacing

Space plants roughly 4-6 inches apart, with rows about 12-18 inches apart

Seed & Germination

For seed starting, the listed germination time is Typically 5-14 days from seed when conditions are suitable and the seed depth is About 1/4-1 inch depending on seed size. The listed time to maturity is Typically 45-120 days depending on cultivar and growing conditions. Use these values as general reference points and adjust for local climate, seed source, and growing conditions.

Germination

Typically 5-14 days from seed when conditions are suitable

Germination temperature

Leek seed germinates well under cool to mild conditions, commonly around 60-75°F, with steady moisture

Seed depth

About 1/4-1 inch depending on seed size

Sowing method

Start leek seed in containers or nursery beds for later transplanting, or direct sow where the growing season is long enough; transplant young plants deeply enough to encourage long blanched shanks

Start indoors

Optional for crops that tolerate transplanting; otherwise direct sow

Transplanting

Transplant after hardening off when temperatures suit the crop

Harvest & Propagation

Days to maturity

Typically 45-120 days depending on cultivar and growing conditions

Harvest

Harvest when stems have reached the desired diameter and usable length; mature leeks are commonly lifted by loosening the soil around the base to avoid damage

Propagation

Primarily propagated by seed and commonly started in containers or nursery beds before transplanting

Seed saving

Leeks are biennial and must overwinter or be replanted to flower in their second season; allow flower heads and seed capsules to mature and dry before collecting, and isolate from compatible Allium ampeloprasum types to reduce cross-pollination

Pollination

Leeks flower in their second year and are primarily insect-pollinated; flowering plants can cross with compatible Allium ampeloprasum types

Garden Information

Common pests

Onion thrips, leek moth, onion maggots, aphids, cutworms, slugs, and other allium-feeding pests

Common diseases

Downy mildew, rust, white rot, purple blotch, basal rot, and other fungal or bacterial diseases

Uses

Edible white stems and green leaves for soups, stews, sautés, roasting, braising, stocks, pies, and other savory dishes