Leek Growing Guide: from seed to kitchen

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.