Leek Seeds

How to Grow Leek

The essential guide to growing leek from seed; with notes on germination, cultivation, harvest and even kitchen uses.

• Autumn leeks (e.g. ‘Musselburgh’, ‘Bulgarian Giant’) – thicker shanks with a mellow, sweet-onion flavour; perfect in pies, frittatas and roasted veg trays. These varieties will hold well into winter as well.
• Winter / overwintering leeks (e.g. 'Blue Solaise', 'Durabel') – stocky, blue-green leaves, very frost-hardy; lend rich depth to slow soups, stews and leek-and-potato classics.
• Baby / bunching leeks – most varieties are suitable for baby leeks, just harvest pencil-thin; add delicate onion notes to omelettes, stir-fries and tapas platters.

Seeds per Gram: ≈ 300 – 350 seeds

Germination Temperature: 18 – 23 °C (emergence in 10 – 14 days)

Feed Requirements:

• Heavy feeder.
• Before sowing incorporate 5 cm compost plus a complete organic fertiliser (approx. 100 g m⁻²).
• At transplanting: dust furrow with additional fertiliser.
• Mid-season: side-dress with blood & bone or liquid seaweed to maintain steady growth.

Growing Notes:

Climate & Timing

• Temperate / cool zones: sow late winter–early spring for summer leeks; sow mid-summer for winter harvest.
• Sub-tropics: sow autumn for winter harvest; avoid humid wet-season.
  Leeks relish cool, moist conditions and tolerate light frosts.

Sowing & Transplanting

• Seed trays: sow 5 mm deep, fairly thickly in punnets or 10 – 12 seeds per 10 cm pot. Keep moist. Once seedlings resemble thin grass (8 – 10 weeks), trim tops to 8 cm and gently tease apart and transplant into garden.
• Direct sow: 5 mm deep, 10 cm apart in rows 30-45 cm apart; thin to strongest plants.
• Planting out: dibble holes 10 cm apart; place one seedling in each and water to settle (don’t back-fill). As plants grow, gradually fill holes or hill soil around stems to blanch and lengthen the white shank.

Water & Soil

• Require fertile, free-draining loam (pH 6.2 – 7.0) with reliable moisture.
• Water deeply once top 5 cm soil feels dry.
• Mulch thickly to conserve water and suppress weeds.

Cultural Tips

• Maintain weed-free beds; leeks dislike competition.
• For extra-white stems, add a sleeve of cardboard tube or mulch collar around each plant three weeks before harvest.

Common Problems & Fixes:

• Poor germination: seed older than two-three years loses vigour—use fresh each season.
• Rust (orange pustules): ensure full sun, good airflow and avoid excess nitrogen; remove affected foliage.
• Onion thrips / aphids: hose off or apply insecticidal soap; encourage lacewings and ladybirds.
• Bolting: caused by seedling cold shock or moisture stress—sow/plant after risk of hard frost, keep irrigation even.

Harvesting & Storage:

• Harvest leeks any time stems reach 15+ mm diameter.
• Lift with a garden fork and shake soil away.
• Leave roots on until kitchen prep to keep stems turgid.
• In most regions leeks hold in-ground through winter—pull as required.
• For short storage, wrap cleaned stems in a damp cloth inside a perforated bag; refrigerate up to two weeks.
• Longer term, slice and blanch 2 min, then freeze for soup bases.

Nurture leeks with rich soil, steady water and gentle hilling, and these cool-season stalwarts will reward you with sweet, snowy stems that carry Australian kitchens from summer barbies right through the chilliest stew season.