Leeks are a valuable addition to the garden because they can be used instead of pungent storage onions from October until April. Even in heavy soils, leeks are easy to grow and have lots of flavour. Continue reading to learn how to grow leeks from seed.

Allium ampeloprasum var. porrum
Family: Amaryllidaceae

Easy, but slow. Transplanting is required.

Season & Zone
Season: Cool season
Exposure: Full-sun
Zone: Winter harvest leeks are hardy to Zone 7.

Start summer/fall harvest leeks 6-8 weeks before the last frost date, in flats indoors. Start winter harvest leeks indoors from March to mid-June. In mild winter areas, start them in a humus-rich nursery bed outside, and then transplant. Optimal soil temperature: 10-25°C (50-75°F). Seeds should sprout in 10-16 days.

In flats: Sow seeds 5mm (¼”) deep, about 1cm (½”) apart. Transplant when 20cm (8″) tall. Space 20cm (8″) apart in rows 45cm (18″) apart. Rows can be as narrow as 20cm (8") if planting in raised beds or other situation where weeding will be simple.

Ideal pH: 5.-6.5. Leeks have short roots, so the benefit from fertile soil with lots of compost and ½ cup balanced organic fertilizer worked in beneath each 2m (6′) of row. Traditional garden wisdom recommends using a dibber to make holes 15cm (6″) deep. Transplants are then set at the bottom of the hole and the hole is left unfilled – rain will fill it in as the leek grows. To blanch further up the stem, hill soil up around the stem as the leek grows, or mulch with straw.

However, the wise and much loved garden writer Linda Gilkeson asserts that there is no need to plant leeks into holes or trenches. She recommends transplanting the seedlings only at the depth of the soil plug they grow in. They will still produce nice, tall, blanched shanks, with no soil grains between the leaves.

In late fall, mulch around leeks as high up the stems as possible. If the forecast is for weather below -10° (14°Ï‚ cover them with a blanket or tarp.

Days to maturity: From transplant date.

Dig at any size, as needed. If winter harvest leeks freeze solid, wait until they thaw out during a warm spell to harvest.

Seed Info
In optimal conditions at least 65% of seeds will germinate. Usual seed life: 1 year. Per 100′ row: 240 seeds, per acre: 70M seeds.

Companion Planting
Grow leeks with beets, carrot, celery, onions, and spinach. Avoid planting near beans and peas. Leeks help repel carrot rust flies.

More on Companion Planting.