How to grow leeks

Leek seeds are widely available in garden centres and from online seed suppliers. Young plants may also be available in spring and early summer, although the choice of varieties will be more limited.

Leeks sown indoors in late winter can be planted outside in mid- to late spring 

Keep the seedlings warm (above 10°C/50°F) and in good light, and keep the compost slightly moist. Move into  larger pots/modules if the roots appear from the drainage holes. Young leeks are usually ready to be planted outdoors after about eight weeks, when 20cm (8in) tall.

The prime sowing months for leeks are March and April, either temporarily in a seedbed (for transplanting later – see below) or straight into their final position. You can also sow later-cropping varieties in May and June, for harvesting in winter and spring, as well as fast-growing varieties for harvesting as baby leeks.

Make a shallow drill about 1.5cm (¾in) deep and water along the base, then sow the seeds thinly along its length. Space any additional rows about 30cm (12in) apart. Cover early sowings with cloches or plastic-free fleece if temperatures drop, as cold spells can cause plants to bolt (flower prematurely).

After about two months, when the seedlings are about 20cm (8in) tall, either transplant them to their final position (see below) or thin them out to 15–20cm (6–8in) apart. You can use the plants you remove to make additional rows.

Sowing in a container

Although leeks are best suited to growing in the ground, you could grow baby leeks, or even full-sized leeks, in a large, deep container. Use peat-free multi-purpose compost and follow the sowing advice above. You could potentially grow four or five mature leeks in a pot about 40cm (16in) wide.

Water leek seedlings and young plants until they are established and growing strongly. After that, you should only need to water during prolonged dry spells. Try to avoid wetting the foliage when you water, as this can encourage fungal diseases such as leek rust. Leeks growing in containers need regular watering across the season, as the compost can dry out quickly.

Apply a layer of mulch, such as garden compost, around leek plants to hold moisture in the soil. This also helps to deter weed germination.

Weed regularly so young leeks don’t have to compete for light, water and nutrients. Leek foliage casts little shade, so weeds grow readily around them. Hoe between rows and hand weed close to individual plants, so you don't risk damaging stems with a hoe.

To help produce the characteristic long white base (shank), earth up your leeks as they grow. This simply means drawing up soil around the leek to exclude light. Do this several times, but try not to let soil get in between the leaves. Earthing up also helps to keep the plants more stable during winter storms.