Leeks are a flavoursome winter vegetable that can be steamed or boiled, braised in a cheese sauce and used in soups and stews. Leeks are easy to grow, but need looking after – you need to sow them in containers or a separate part of the garden before moving them to their final position. Sow seed in spring, and you will be picking leeks from autumn to late winter.
For bumper crops you will need to improve the growing area by digging in plenty of compost or well-rotted manure in the autumn.
Leeks are best suited for growing in the open ground, but you could grow several in large, deep containers or raised beds.
Leeks can be either sown directly in the ground outside, or in seed trays (and left outdoors). If you only want a few leeks, it is best to sow in seed trays, then transplant outdoors. Use modular trays and sow one seed per module.
Traditionally, leeks are sown into a seedbed, which is a site away from your main vegetable plot and transplanted later in the season. This is because sowing leeks at their final spacings in your main vegetable plot would take up a lot of room early in the growing season, when you could be growing fast-maturing crops such as lettuce.
Sow seed thinly 1cm (½in) deep in rows 15cm (6in) apart in a seedbed in March and April.
To increase the length of white stem it can be blanched by gently drawing up dry soil around the stem in stages, but try not to allow soil to fall between the leaves.
Water during long, dry spells and weed regularly.
Troubleshooting Growing Problems
Leek rust: This is a fungal disease causing bright yellow spots on the leaves. It is often worse in long, wet spells.
Remedy: Mild attacks of rust won’t harm the plant, but serious infections may cause leaves to shrivel and affect yield. There is no control for rust once you have the infection. Make sure you don’t crowd plants, as this increases humidity and increases the likelihood of infection. Dispose of any badly affected plant material, and don’t grow garlic, leeks or onions in the same spot for three years.
Onion white rot: A soil-borne fungus that can cause yellowing and wilting of the foliage above ground, while rotting the roots and invading the bulb beneath the soil. A white fluffy fungus appears on the base of the bulb and later becomes covered in small, round black structures.
Remedy: There is no chemical cure for onion white rot when it is the soil. It is important to avoid introduction to previously clean sites. It is transported in contaminated soil, for example on tools or on muddy footwear. Take particular care in areas where cross contamination can occur easily, for example on allotments.
Leek moth: This is a relatively new pest of leeks and onions and thought to be mainly concentrated around the south-east coast of the UK, although it has been found further inland and north. Caterpillars tunnel into the leaves, causing whitish-brown patches to develop on leaves. In severe cases, leaves may turn yellow and rotting occurs within them.
Remedy: Once you see the damage, there is nothing you can do to control it. Remove and destroy infected plants. When planting out, cover leeks with horticultural fleece (like Enviromesh) to prevent adult moths from laying eggs.
Start lifting when the leeks are still quite small to ensure a long harvest period. Gently lift from the soil using a fork.
Leeks can remain in the ground through the winter until they are needed.
Some of the plants that like leeks would make terrible menu items but work nonetheless. Strawberries seem to enjoy living next to leeks, and the strong odor of the leeks repels many pests of the berries. Other leek plant companions might be cabbage, tomatoes, beets and lettuce. The leafy vegetables, especially, seem to benefit from the strong scent of plants in the Allium family. One of the best plants that like leeks is the carrot. Carrots are plagued by carrot flies and leeks are eaten by onion flies. When the two plants are near each other, the individual aromas seem to repel each other’s pests. Plus, as root crops, they share in breaking up the soil as they grow, making it loose for better carrot roots and larger leek bulbs. Other plants to try are more attractive. Use calendula, nasturtium and poppies as covers for the leek and repellents due to their pungent herbal flavor and aroma. A side note on what to grow next to leeks should include what not to grow near these plants. Apparently, beans and peas do not thrive near any member of the onion family. As mentioned, there is no real research confirming the usefulness of companion planting, but its tradition is long and storied.