Leeks

Leeks are tasty winter vegetables that are easy to grow, but do take some time and attention – they are usually sown in containers or a ‘seed bed’, then moved to their final position a few months later. Sow seed in spring, and you’ll be harvesting from autumn through to late winter.

Jobs to do now

  • Water during long dry spells
  • Weed regularly around plants

Month by month

Sow

For a bumper crop of leeks, improve the growing site by digging in plenty of garden compost or well-rotted manure, ideally in autumn.

Leeks are best suited for growing in open ground, but you could grow several in large, deep containers or raised beds.

Traditionally, leeks are sown into a seed bed, away from your main vegetable plot, then the young leeks are transplanted in early summer. 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 lettuces. 

During March or April, sow leek seeds thinly, 1cm (½in) deep, in rows 15cm (6in) apart. 

If you don’t have space outdoors or only want a few leeks, you can sow in modules indoors, then transplant outdoors later. Sow one seed per module.

Grow

Grow

To increase the length of white stem, gently draw up dry soil around the plants in stages as they grow, but try not to let soil fall in between the leaves.

Water during long dry spells and weed regularly.

Harvesting

Start harvesting in late summer, when the leeks are still quite small, to increase the cropping period. Gently lift from the soil using a fork.

Leeks can remain in the ground through the winter until they are needed.

Recommended Varieties

Leeks — winter & early spring

Leeks — winter

Common problems

Leek rust
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
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
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.

Recipes

Anthony Worrall Thompson includes leeks in his root vegetable gratin dauphinoise

Nigel Slater adds leeks to his artichoke soup with ginger and walnuts

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.