Allium porrum

Sowing and cultivation tips

Allium porrum seeds germinate best in full sun and fertile, well-drained yet moisture-retentive soil. Start under cover in late winter in modules or trays; transplant sturdy seedlings when the soil is workable and the risk of hard frost has passed. In mild climates, sow in late summer to autumn for overwintering. Space generously to encourage thick stems; check packet guidance for exact distances. Plant deeply or gradually earth up to blanch stems, keeping crowns above soil. Keep evenly moist, mulch to conserve water, and feed lightly during active growth. Weed regularly and protect from strong winds; the crop grows medium-tall and benefits from steady, unhurried growth for the best shafts.

• Sow under cover in late winter; transplant when soil is workable and the risk of hard frost has passed. In mild climates, late-summer to autumn sowings may overwinter.
• Grow in full sun and fertile, well-drained yet moisture-retentive soil; keep moisture steady and mulch to conserve it.
• Plant seedlings deep in holes or shallow trenches and gradually earth up to blanch the stems, keeping the crown above soil.
• Allow generous spacing for thick shafts; follow packet guidance and keep the bed weed-free; provide shelter in exposed sites for this medium-tall crop.
• Grown for its edible leaf-bases (stems); harvest once shafts reach a usable size.

How do you grow leeks (Allium porrum) from seed?

Allium porrum seeds grow best in full sun and fertile, well-drained yet moisture-retentive soil. Start seeds in modules or a seedbed, then transplant to their final position once the soil is workable and the risk of hard frost has passed. Leeks are medium-tall plants, typically maturing to 30–60 cm, and benefit from generous spacing to develop thick, tender shanks. Keep growth steady with consistent moisture and light feeding. Good weed control and mulching help conserve moisture. For straight, long stems, plant deeply or use earthing up as they grow. Harvest timing depends on variety and sowing window.

When should I sow leek seeds?

Sow under cover in late winter for planting out in spring (Northern Hemisphere) / autumn (Southern Hemisphere), once the soil is workable and danger of hard frost has passed. In mild climates, late summer to autumn sowings can be grown on for overwintering and harvesting the following cool season. For direct sowing, wait until the seedbed has warmed and is no longer waterlogged. Staggered sowings extend the harvest period, from early varieties for summer/autumn use to later types for winter. Always adjust timing to local frost patterns and soil conditions rather than calendar dates.

How do I start leek seeds indoors, and how deep should I sow them?

Sow Allium porrum seeds 0.5–1 cm deep in trays, modules, or pots filled with fine, moist seed compost. A cool to mild germination range supports even sprouting; provide bright light to prevent leggy growth. Keep the medium evenly moist but not waterlogged, and thin or prick out to give seedlings space. Grow on until they are sturdy, with several true leaves and a thickness similar to a pencil lead. Harden off gradually before planting outside. Early indoor starts help achieve large stems by giving a head start before outdoor conditions settle.

Can I direct sow leeks after frost, and when do I transplant seedlings?

Yes—direct sow after the last hard frost when the soil is workable, covering seeds lightly and keeping the bed moist. Thin to the strongest seedlings. For transplants raised indoors or in a nursery bed, plant out once the risk of hard frost has passed and seedlings are robust, with 3–4 true leaves. Traditional practice is to “dib” holes 12–15 cm deep, drop seedlings in, and water to settle soil around roots, encouraging a long, tender shank. Space generously—typically 15–20 cm between plants in rows 30–45 cm apart—following packet guidance for the variety.

What soil, spacing, and care do leeks need, including watering and feeding?

Leeks prefer fertile, well-drained, moisture-retentive soil enriched with mature compost. Avoid fresh, high-nitrogen manures at planting, which can cause soft growth. Provide full sun and generous spacing—about 15–20 cm between plants and 30–45 cm between rows—to promote thick stems and good air flow. Keep moisture steady, especially in dry spells; an organic mulch helps reduce evaporation and suppress weeds. Feed lightly during active growth if soil fertility is modest. Remove competing weeds carefully to protect shallow roots. Healthy plants grown at a steady rate produce the best flavor and texture.

How do I blanch leeks by earthing up, and can they grow in containers or overwinter?

For long white shanks, gradually earth up soil or add mulch around stems as they thicken, keeping foliage tips above the surface and soil out of the leaf bases. Alternatively, plant deeply at transplanting. Leeks grow in containers if the pot is deep (at least 30–35 cm) and filled with a rich, free-draining mix kept evenly moist; feed modestly over the season. In mild climates, late summer to autumn sowings can overwinter outdoors with mulch for protection. In colder areas, choose hardy varieties and provide extra cover in severe cold. Note: alliums can be harmful to pets if ingested.

Growing information on this site is general and compiled from horticultural references and practical experience. Conditions vary with microclimate, soil structure, drainage, and seasonal patterns. Use local climate cues—soil temperature, last frost timing, and day length—to adjust timing and methods. For precise details such as sowing depth, spacing, and handling, refer to the relevant product page, which provides the most specific instructions for the variety listed.

Cultivating leeks from seed

Allium porrum seeds yield long-season leeks valued for their mild, savoury stems. Sow in trays or modules 6–12 mm deep in fine, moist compost, keeping evenly warm for steady germination. Transplant after last frost when seedlings are 15–20 cm tall and pencil-thick; harden off gradually. Plant into fertile, well-drained soil in full sun; space 15–20 cm apart in rows 30–40 cm, setting seedlings deep or in dibbled holes to encourage long shanks. Water consistently and mulch to retain moisture; hill gently as plants develop. In mild climates, autumn sowing may be possible for overwintering. Harvest when stems reach desired girth, typically many weeks after transplanting. For succession, stagger sowings when soil is workable. Choose varieties matched to your season length; early strains mature sooner, while late selections stand firm in colder spells. Rotate beds to reduce pest and disease pressure, and store seed cool and dry for best longevity.