Growing Leeks in the UK: A Beginner's Guide

Why are leeks such a good crop for UK gardens?

If you grow one thing to see you through the hungry months, make it leeks. They are the classic British winter staple for a simple reason: they are tough. Properly, seriously hardy. While the rest of the veg patch has collapsed into brown mush by December, leeks just stand there in the cold, green and unbothered, waiting for you to want them.

That is the real magic of them. You don't harvest leeks and store them. You leave them in the ground as living, self-storing plants and lift them one at a time, fresh, from autumn all the way through winter into early spring. A hard frost doesn't hurt an established leek. If anything it sweetens the flavour. When there's frost on the ground and nothing else worth eating outside, a row of leeks is about the most reassuring sight a kitchen gardener can have.

They ask very little of you, too. No staking, no fiddly pruning, no daily fussing. Sow, transplant, water them in dry spells, and mostly get out of the way. The one technique worth learning properly is how you plant them out, because that single step is what gives you those long, pale, tender white stems rather than short green stumps.

You don't store leeks. You leave them standing in the ground and lift them fresh, one at a time, right through the winter.

When and how do you sow leeks?

You've got two easy routes, and both work well in the UK.

The tidy, reliable one is to sow indoors or under cover from February to March. Fill modules or small pots with peat-free seed compost, sow a few seeds per cell, and keep them on a bright windowsill, in a greenhouse or in a cold frame. They germinate happily at fairly low temperatures and don't need much heat. After roughly eight weeks you'll have thin, grassy seedlings ready to move on.

The old-school allotment route is to sow outdoors in a spare seedbed from March to April. Sow thinly in shallow drills, keep the bed weeded and watered, and let the seedlings grow on where they are until they're big enough to lift and transplant to their final home. It's how leeks have been grown on plots for generations, and it saves windowsill space.

If you want leeks that stand deep into winter and spring, you can also sow hardy varieties a little later, in May or June. Whichever route you take, the seedlings are ready for the next stage when they're about pencil-thick and 20cm (8in) tall.

What is the classic leek transplanting technique?

This is the bit that makes leeks leeks, and it's the headline skill worth getting right. It looks odd the first time, but it's simple enough once you've done a row.

The goal is a long white shank, which is the pale, mild, tender part everyone actually wants to eat. The green top is fine for stock, but the white is the prize. You get it by growing a good length of the stem underground, in the dark, so it never turns green. And the way you do that is to plant each seedling into a deep, narrow hole and simply let water, not soil, settle it in.

1. 1

   Lift the seedlings

   When they're pencil-thick and about 20cm tall, gently lift them from their modules or seedbed, teasing the roots free without snapping them.

2. 2

   Trim, if you like

   You can trim the straggly roots back to about 2.5cm (1in) to make planting easier. Trimming the very tips of the leaves is an optional old habit some growers swear by to reduce wind-rock and water loss; skip it if you'd rather not.

3. 3

   Dibber a deep hole

   Using a dibber or a thick trowel handle, make a hole about 15cm (6in) deep and 5cm (2in) across. Go deeper, up to 20cm, if you want an even longer white shank.

4. 4

   Drop one seedling in

   Lower a single leek into each hole so most of the stem sits below ground and just the leaf tips poke out. Don't push it in hard, and don't backfill the hole with soil.

5. 5

   Puddle it in

   Fill the hole to the brim with water from a can. That's it. The water washes a little fine soil down around the roots and settles the plant. The hole itself stays largely open.

How far apart should leeks be spaced?

Give them room and they'll size up nicely. Space the plants about 15cm (6in) apart, and a touch more, up to 20cm, if you're after really fat leeks. Keep rows around 30cm (1ft) apart so you can hoe between them and draw soil up later.

If it's slim, elegant baby leeks you're after, plant them closer, around 10cm apart, and lift them young.

How do you get a longer white part?

Two things do it, and they stack.

First, that deep planting hole. Starting the stem 15 to 20cm underground means a good chunk of it is blanched from day one. Second, earthing up as the plants grow. Every few weeks through the season, draw dry soil up around the stems with a hoe, a little at a time, keeping it out of the centre of the plant where the leaves fan out. Each bit of stem you cover is another bit that grows pale rather than green. Some allotmenteers even slip a collar of cardboard tube around each stem for extra length. It's not essential, but it's the trick behind those show-bench leeks with a foot of white.

What soil and site do leeks need?

Leeks aren't fussy, but they reward a decent bed. They like an open, sunny spot and a fertile, reasonably firm soil that holds moisture without waterlogging. Before planting, work in a couple of bucketfuls of garden compost or well-rotted manure per square metre. If you make your own, this is exactly the kind of hungry crop it's for. Our guide on how to compost at home covers getting a good supply going.

Firm ground matters more for leeks than for many crops, because a loose, fluffy bed lets tall plants rock about in autumn gales. Tread the bed lightly before you dibber your holes.

How much watering do leeks need?

Keep the young transplants watered until they're clearly established and growing away, which usually takes a couple of weeks after that first puddling-in. After that, leeks are fairly drought-tolerant and only really need watering during long dry spells in summer. When you do water, aim at the soil rather than the foliage. Wet leaves sitting damp overnight make fungal problems like rust more likely.

When and how do you harvest leeks?

Here's the payoff. Full-size leeks take roughly six months from sowing, so an early sowing gives you leeks from late summer or autumn onwards. And then they simply wait for you. There's no rush, no glut, no scramble to preserve a harvest. You lift them as you cook.

To harvest, don't just yank the leaves. Ease a fork in alongside the plant, lever gently to loosen the roots, and lift the whole leek clear. Trim the roots and the toughest green tops, and you're done. Because they're so hardy, you leave the rest standing in the ground and come back for the next one whenever you need it, right through the coldest months and, with late varieties, into spring. It's about as close to a living larder as the veg patch gets.

What problems affect leeks in the UK?

Leeks are healthy plants on the whole, but a few things are worth knowing.

The two allium grubs. The main pests are a pair of tunnelling grubs, and the good news is one defence handles both. Leek moth caterpillars feed inside the leaves and stems, leaving pale window-pane patches and tunnels, mainly in May-June and again August-October. Allium leaf miner maggots bore into the foliage and stems, with the adults laying eggs around March-April and again September-November. For both, the fix is the same: cover the crop with insect-proof mesh (fine mesh, around 0.6mm) through the risk periods so the adults can't reach the plants to lay. Rotate where you grow alliums each year too, or emerging adults can simply pop up underneath the mesh.

Leek rust. You'll almost certainly meet this. Bright orange, dusty pustules appear on the leaves, usually from mid-summer through autumn, and it's incredibly common in UK gardens. A light case is largely cosmetic. The leeks are still perfectly good to eat once you peel off the outer layers. A heavy attack, though, can shrivel the leaves and knock back growth, so space plants well for airflow, go easy on high-nitrogen feed, clear away old debris, and choose rust-resistant varieties if it's a yearly headache. There are no fungicides for home gardeners, so prevention is the whole game.

White rot. This is the serious one, thankfully far less common. Onion white rot is a soil-borne fungus that rots the roots and base and turns the foliage yellow and wilting. It lingers in the soil for years, so if it appears, don't grow leeks, onions or garlic in that patch for a long time. Rotating your alliums around the plot is the best insurance. The same care applies to the whole onion family, and you'll find more on that in our guide to growing onions.

Which leek varieties should a beginner grow?

Leeks are usually split by season, and it's worth growing a couple of types so your harvest stretches.

Early (autumn) varieties are quicker and more tender, ready from late summer into autumn, but they're less hardy, so eat them before deep winter. Maincrop and late varieties are the hardy workhorses. Slower to bulk up, but built to stand out in the cold through winter and into spring without protection. For a first year, a reliable maincrop is the safest pick, because standing hardiness is the whole point of a leek. Add an early type once you're hooked and want leeks a bit sooner.

Related guides and tools

Once your leeks are in, it's worth planning what shares the bed and what follows them. A few places to go next:

• Browse the full vegetable growing guides for the rest of the patch.
• Grow the wider onion family with our guide to growing onions in the UK.
• Feed that hungry leek bed with homemade compost using how to compost at home.
• And to get every sowing and transplanting date right for your area, our planting calendar lays out the whole year at a glance.