Allium
How to grow leeks
Allium ampeloprasum (Porrum group)
Leeks are sown in spring, transplanted in June or July and pulled from September right through to April, which makes them the most useful winter vegetable in a UK garden. Give them full sun and deep soil with plenty of compost in it. Success comes down to two things: dropping pencil-thick seedlings into deep dibber holes so the shaft blanches, and steady water and feed through July and August while they bulk up.
- Hardiness
- Fully hardy, stands through winter
- Position
- Full sun
- Soil
- Deep, rich, moisture-retentive
- Ideal pH
- 6.5 to 7.5
- Water
- Moderate, water in dry spells after transplanting
- Feeding
- Heavy feeder
Sowing and planting leeks
WhenSow Jan to Apr; transplant Jun to Jul; harvest Sep to Apr
Starting off
Sow in a seed tray or modules at 10 to 15 °C in Jan to Mar, 1 cm deep, 4 seeds per module, germinating in 14 to 21 days; or direct in a seedbed outside in March to April. Transplant in June to July when 20 cm tall and as thick as a pencil, trimming roots to 2 cm; no need to trim tops.
Spacing and planting
Transplant 15 cm apart in rows 30 cm apart for large shafts, or 10 cm each way for slender baby leeks. Drop pencil-thick seedlings into 15 to 20 cm deep dibber holes, water in and leave the soil to fall back. Baby leeks are worthwhile in a 30 cm deep container; full-size leeks are not.
Varieties worth growing
- Musselburgh
- The old Scottish standard: short, thick shafts, very hardy and dependable on any soil for pulling from December to March.
- Oarsman F1
- Long, uniform mid-season shafts that bulk up quickly, with good tolerance of rust and little tendency to bolt.
- Bandit
- A late, blue-green leek that stands hard frost and holds in the ground until April without running to seed.
- King Richard
- Early and very long in the shaft, ready from September and the best choice for close-planted baby leeks. Not hardy enough to stand the winter.
- Below Zero F1
- Bred for winter hardiness and rust tolerance, for cold gardens where other leeks turn to mush in January.
Leeks month by month
Timings are for central England. Allow two weeks later in the north and on cold, heavy soil.
- January
Lift as needed. Sow an early variety in modules indoors for September leeks.
- February
Sow in modules or a seed tray under cover. Keep lifting.
- March
Sow under cover, or outdoors in a seedbed late in the month. Lift the last of the mid-season leeks.
- April
Last sowing outdoors. Lift remaining leeks before they throw a flower stalk and heel them in somewhere shaded.
- May
Weed and water the seedlings. Prepare the bed with compost.
- June
Transplant pencil-thick seedlings into 15 to 20 cm dibber holes and water them in. Mesh on at once where leek moth is about.
- July
Finish transplanting. Water in dry spells. First top-dress in the middle of the month.
- August
Second top-dress late in the month. Draw a little dry soil up the shafts to lengthen the white.
- September
Pull the first early leeks. No more feeding. Mesh stays on for allium leaf miner.
- October
Lift as needed, loosening with a fork first. Earth up once more.
- November
Lift as needed. Clear rusty and yellow outer leaves.
- December
Lift as needed. Before a long freeze, dig a few and heel them in near the house.
Feeding leeks
A hungry crop that sits in the ground for up to ten months. Compost and a base dressing at transplanting, two top-dresses in summer, then nothing from September so the plants go into winter firm.
Hungry and long in the ground, work in organic matter and feed steadily with a nitrogen-leaning feed through summer for long, thick shafts.
Feeding plan
Winter or spring before transplanting
Garden compost
A 5 cm layer forked in or left on the surface. Well-rotted manure does the same job.
A week before transplanting, June
Fruit & Vegetable Fertiliser 4-5-6
100 g/m² raked in. With rows 30 cm apart that is 30 g per metre of row (100 x 0.3).
Mid July
Organic Nitrogen Fertiliser 13% N
25 g/m², the low end of the label for leafy crops: about 8 g per metre of row, scattered beside the plants and watered in.
Late August
Fruit & Vegetable Fertiliser 4-5-6
50 g/m², or 15 g per metre of row. That brings the season's total to 150 g/m², the label maximum, so no more after this.
September onwards
Nothing
Late nitrogen gives soft growth, splitting bases and more rust.
Signs to watch
Pale, thin shafts and slow growth in July
Nitrogen short
Balanced feed every 3 to 4 weeks
Bolting with a flower spike
A cold spell after early transplanting, not feeding
Sow later or fleece
Bulbous, splitting bases
Late nitrogen and uneven water
Ease off feeding from September
Pests, diseases and problems
Bright orange, raised pustules on the leaves from late summer
Leek rust, encouraged by damp weather, crowding and soft, nitrogen-rich growth
Usually cosmetic: strip the outer leaves in the kitchen. Keep to 15 cm spacing, stop nitrogen by early September, clear all debris after harvest and grow a tolerant variety such as Oarsman F1 or Below Zero F1.
Pale brown and white patches on the leaves, then tunnels into the shaft that rot
Leek moth caterpillars, feeding in May to June and again in August to October; commonest in southern England
Cover with fine insect mesh from transplanting, edges buried. Pick off any small cream cocoons on the leaves. Plants that are attacked lightly often grow through it.
Lines of white dots on the leaves in autumn, then split, twisted plants with brown pupae between the layers
Allium leaf miner; the autumn generation lays eggs from September to November
The same mesh, kept on from September to the end of November and again in March and April over any late crop.
Plants yellow and wilt, white fluffy mould with black dots at the base
Onion white rot in the soil
Bin affected plants with the soil round the roots, and grow no leeks, onions or garlic on that ground again.
Fine silvery flecking over the leaves in a hot, dry summer
Onion thrips
Water thoroughly; damage fades once the plants are growing strongly in cooler weather. Mesh put on for leek moth keeps thrips numbers down as well.
Harvest and rotation
Harvest and storage
Lift from September when the shaft is 2 to 3 cm across, 30 to 45 weeks from sowing; hardy varieties stand until April. Loosen with a fork, never tug. A 3 m row of 20 plants gives 5 to 6 kg. They do not store lifted; heel in a trench near the kitchen before hard frost, or blanch and freeze.
Rotation and companions
Rotation: allium group, 3 to 4 year gap; the long cropping season means it often follows early peas or broad beans in the same year. Keep away from beans, which resent alliums, and from brassicas that shade the slim seedlings.
Good to know'Dib and drop' transplants into deep holes and water in without backfilling, this blanches the long white shaft.
Growing leeks in pots
Full-size leeks are not worth a pot: they need depth, they tie the container up from June to March and each plant gives one stem. Baby leeks are different. Sow King Richard thinly in a container at least 30 cm deep from March to May, thin to 3 cm apart, and pull at spring onion to finger thickness after 12 to 14 weeks. Use peat-free multipurpose compost with the 4-5-6 mixed in at 5 g per litre if the compost is not fresh, and never let it dry out.
Leeks: common questions
When should I transplant leeks?
Transplant in June or July, when the seedlings are about 20 cm tall and as thick as a pencil. Make a hole 15 to 20 cm deep with a dibber, drop one seedling in, fill the hole with water and leave the soil to settle back by itself.
Do I need to earth up leeks?
Not if you planted them in deep dibber holes, which blanches most of the shaft for you. Drawing dry soil up the stems once or twice in late summer adds a few more centimetres of white, but keep it out of the leaf joints or the leeks will be gritty.
Why are my leeks thin?
They were sown or transplanted late, planted too close, or went short of water and nitrogen in July and August, when leeks do most of their growing. Plant by mid July at 15 cm apart, water in dry spells and top-dress in summer. Thin leeks are still good to eat and will fatten a little in a mild autumn.
Sources
Growing information on this page was checked against these references in November 2026. Feeding rates are Dr Forest label rates.