Tips on how to grow leeks
With their sweet, mild, oniony flavour, leeks add a silky texture to soups, stews and quiches and are divine when roasted. They’re a great alternative for people who find onions too strong and improve our digestive health, too.
SOW AND GROW
Sow seeds: February to May in warm areas; September to April in cooler areas.
Transplant seedlings: September to March in warm areas; September to February in cooler areas.
Position: Full sun, six-plus hours a day.
Harvest: 12-26 weeks from seed.
GET STARTED
Sow leeks direct or in trays from late summer to late autumn in warm areas and from early spring to mid-autumn in cool areas.
Seedlings can be planted from early spring to early autumn in warm areas and early spring to late summer in cooler areas.
If you want to have fat leeks ready to harvest in winter though, you will need to plant them in spring.
STEP-BY-STEP
To give leeks the best start, sow seed shallowly onto the surface of seed trays or prepared garden soil. The advantage of using seed trays is that leeks are initially quite slow growers and are always in danger of being out-competed by weeds in the garden. Space seeds at least 5cm apart and lightly cover. Seed should germinate in 10–14 days. Seedlings can be transplanted into the garden when they’re about 20cm tall. In the garden they need to be spaced 20cm apart.
GROWING TIPS
Before planting prepare your soil with sheep pellets and compost. Leeks appreciate good drainage so add pumice or sand if you have heavy clay.
When transplanting leek seedlings, the key for fat leeks is to plant them deeply. Use a bamboo stake, empty beer bottle or dibber to make 10cm deep holes, and drop a seedling into each one. Pack the soil in around the seedlings and water in well.
Keep the soil as moist as you can for the first 7–10 days after transplanting, and check transplanted leeks every few days after planting as cats and birds have a habit of scratching the spindly seedlings up. Once seedlings thicken up, continue to mound up the soil around their stems for blanched white bases, but be careful not to mound it up too high or you’ll end up with soil embedded between the pale layers at harvest. Feed every fortnight with liquid plant food.
Harvest leeks when stems are around 2.5cm in diameter (although if yours don’t fatten up just re-brand them as gourmet baby leeks!). To avoid snapping off the flag (the leafy green top), carefully dig out using a trowel rather than yanking them out.
STANDOUT VARIETIES
Scottish heirloom ‘‘Musselburgh’’ is one of the most popular varieties and produces long, green shanks. ‘‘Winter Giant’’ produces heavy, thick stems and is suitable for growing over winter into spring. ‘‘Lungo della Riviera’’ produces long, slender, tender stems and is great for growing as a mini leek, or try shorter-shanked ‘‘Mini Speciality’’ for smaller gardens.
TROUBLESHOOTING
Increasing day length can trigger leeks to bolt to seed around October or November. Wait until autumn to sow leeks in the warmest, northern areas. Conversely, bolting can occur in temperatures below 5°C when the plants are taller than 10cm. Avoid planting seed too early in spring if this happens. Leeks can be attacked by aphids, and yellow or black dots on plants may indicate the presence of thrips. Both are more likely if this crop dries out so be vigilant with irrigation.