Growing Leeks

The Leek [ Allium ampeloprasum var: porrum ], is one of our hardiest and most versatile vegetables. A member of the onion family it closely related to elephant garlic. The leek is a good vegetable for cooler climates like ours, is easy to grow and can fill the harvest gap when there is little else in the garden. By choosing the right varieties, and sowing from February to August, leeks can be harvested for most of the year. They will stand in the ground through the worst of the winter weather. Leeks are a biennial and will produce seedheads in their second year. They can also produce baby leeks on the seedhead called grass or pips. These can be overwintered undercover and planted the following spring. The grass or pips are what exhibition leek grower use to grow their show leeks. Sometimes leeks produce small bulbs at the base of the old leek stems, these can be eaten like baby onions or shallots.

Soil Preparation

Leeks prefer a sunny well drained site but are not too fussy about soil type. They do like a rich soil and as they are in the ground for a long time, adding lots of well rotted garden compost will make them happy. Dont use manure to enrich the soil, unless it was dug in for the previous crop or in the year before and well rotted. Work the soil till it is fine and crumbly. A well balanced fertilizer can be added a week or so before planting out.

Sowing under glass

You can get an early start by sowing in seed trays or modules inside in Feburary. Sow thinly into trays of a good quality moist compost, cover with a quarter inch of sieved compost or vermiculite. Keep warm till the seed germinates, usually 14 – 21 days. Then place in good light. They dont need much heat to grow on, but keep frost free. You can also sow one seed into individual modules of moist compost, grow on in the same way. They will be ready to plant out from mid April, through June, depending on sowing date and variety, or when about 6 inches high.

Seed Bed Sowing

Leek seed can be sown outside from late March, depending on the weather and soil conditions, in a seed or nursery bed. Rake the soil to a fine tilth and sow seed thinly a quarter inch deep in rows 4 inches apart, leave till well grown and ready to be planted out. The use of cloches can help.

Direct Sowing

The leek seed can also be sown direct where they are to grow. Rake the soil to a fine tilth and sow a quarter inch deep in rows about 9 inches apart. When the seedlings are 3 inches high, they can be thinned to 2 inches apart. When the seedlings reach 6 inches high, thin again to leave 6 inches between plants. The thinnings can be used to fill gaps or make another row. Dont attempt any direct or outdoor sowings till the soil has started to warm up, and can be easily worked.

Planting Out from Trays and Modules

I would wait till the worst of the frosts are behind you before planting your young leeks out. Make sure you harden them off really well and hopefully the weather should be warm enough for them to go out in April. When your seedlings are ready to plant out in their prepared growing bed, carefully lift the seedling out of their growing container and using a trowel or a dibber to make a hole and plant the leek a few inches lower than it was growing in the tray or module, see the photo below. Planting the leeks deeper will give more white stem on the leeks as it blanches by being under the soil. The leaves and roots can be trimmed before planting. Space the plants 6 inches apart in rows about 8 inches apart. You can use closer spacings, then pull every other leek to use as a young veg, or bigger spacings for bigger leeks, whatever suits you. Always plant the young leeks with the leaves all facing along the row and not across. This will help make weeding easier. Water well to bed in the young plants, dont back fill with soil as it may get in between the leaves.

Planting Out from a Seed Bed

See also How to grow leeks from seed

Water the seed bed and lift the young leeks carefully, it is usual to trim the leaves and roots of the outdoor raised leek seedlings before planting out. It make the seedlings easier to plant and cuts down on moisture loss due to transplanting. Use a dibber to make holes about 4 – 6 inches deep and 6 – 8 inches apart. Drop a leek into each hole and instead of filling with soil, use a watering can to water the seedling in. The water will pull sufficient soil into the planting hole and prevent soil getting in between the leaves. Again planting distances will depend on the size of leeks you wish to produce.

Growing On

Leeks require little tending. Water well in dry weather, and keep weed free. If the foliage or flag as it is called grows too long and trails on the ground, it can be trimmed, this can be helpful in a windy or exposed site. Mulching will help to retain moisture and help with weeds. Keeping your growing leeks weed free can help prevent attacks from rust.

Feeding.

If you added well rotted manure in the Autumn and top dressed with a general fertiliser a week or so before planting out, your leeks should not need extra feeding till early June. From June till August, I would give the leeks a liquid feed, every 2 weeks. Try using a seaweed based feed, or make your own liquid feed from nettles, comfrey or borage, or a mix of all three. In mid August, a topdressing with blood, fish and bone, watering it in well will see them through till harvesting.

Harvesting.
Your leeks can be harvested from the thickness of a pencil, through to full maturity. Although they are hardy, if heavy frost is forecast you can cover part of the row with straw or fleece so you can lift them easily if the ground is frozen. Alternatively, lift some leeks and heel them inside in a greenhouse or polytunnel if the ground is going to freeze hard. The leeks can last for weeks heeled in. Leeks will last for a couple of weeks after harvesting if kept in a cool place. They also freeze well.