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.
Ideal pH: 6.0-6.5. Aim for a soil with ample drainage and lots of organic matter. Add compost and lime at least 3 weeks prior to planting. One cup of balanced organic fertilizer per 3m (10′) of row will give adequate nutrition. Seedlings should be hardened off by reducing water and putting the plants outdoors 2 or 3 days before transplanting. This will help to prevent transplant shock and premature bolting. Regular watering is essential to prevent leaves from developing a bitter taste.
Dig at any size, as needed. If winter harvest leeks freeze solid, wait until they thaw out during a warm spell to harvest.
In optimal conditions at least 65% of seeds will germinate. Usual seed life: 1 year. Per 100′ row: 240 seeds, per acre: 70M seeds.
Diseases & Pests
Crop rotation is important for disease prevention. Tip burn (tips of leaves turning brown) is caused by a calcium deficiency. If you have limed, tip burn can be caused by nutrient imbalances or lack of moisture. Slugs are a problem in early and late plantings, so clean up their hiding places, and only water in the morning.
Grow leeks with beets, carrot, celery, onions, and spinach. Avoid planting near beans and peas. Leeks help repel carrot rust flies.
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