Growing Leeks from Seed

There are two traditional ways to grow leeks. The first of these is growing leeks from seed; the second is to buy “starts” which are essentially leek seedlings. Growing leeks from seed is just as effective as the other method, and can work out a lot more cost-effective. The one downside is you’ll want to plan ahead in order to make sure your seedlings are large enough to plant out as the season begins.

Leeks are one of my favourite vegetables, both to eat and to grow. They’re tremendously hardy, and are capable of dealing with a surprising amount of cold and/or rain. This makes them an ideal crop for those of us living in cooler climates, and also helps to explain why Wales is such a worldwide hotspot for leek growing.

Indeed, leeks will even survive under snow for a period of time, meaning that they can provide fresh food throughout the year. Lastly, unlike many other crops that have a “season”, and must all be harvested at once, leeks can be eaten at almost any size. Tiny youngsters can be fried up early in the season, while larger specimens can be left in the ground all through the winter.


Planting Leek Seeds

Leek seedlings

Leek seeds are matt black in colour and just a few millimetres in length, so they’re not the easiest seeds to handle. As they grow, the roots extend pretty rapidly, and the seedlings are best planted out at a reasonable size. This means that the best solution for planting seeds tends to be very deep seed trays. Ideally forget about standard low trays, and instead find one that offers some 3″ or more of compost depth.

Gently fill the seed tray with good-quality seed or multi-purpose compost, then gently press a second seed tray ontop. This will firm down the compost, and leave a small gap between the surface of the compost and the rim of the seed tray.

Next, gently scatter the seeds over the surface of the compost, then add a further thin layer of compost ontop. Personally I add only a few millimetres, and use a soil sieve to ensure the compost through which the seedlings need to push is as fine as possible.

Next, water the compost. This is most easily done by popping the container into a tray or bathtub filled with water, then letting the compost gently soak up the moisture. This is preferable than watering from above, as this can dislodge the fine seeds, causing them to germinate in clumps rather than spread out.

The seed tray can be placed on a south-facing windowsill or a greenhouse, making sure that the compost is not allowed to dry out. I like to use seed tray covers, which act as mini greenhouses; both keeping in the moisture as well as gently raising the temperature.

Leek seeds germinate quite quickly in my experience, and may start showing their heads in as little as a week or so.

Leek seedlings are interesting because they germinate “folded over”. The seedlings will reach a point of a centimetre or two above ground, then the seedling will “unfold” – essentially doubling it’s height in a matter of days. Be prepared for this, as any tray cover that you have used will either need to accommodate this growth spurt, or be removed at the appropriate time.

Growing Leek Seedlings

Creative recycling

Leek seedlings are quite undemanding after germination. Keep them watered and offer them as much direct sunlight as possible. While leek seedlings can be planted out at almost any time of year, and at virtually any size, the bigger the seedlings and the warmer the weather the more swiftly they will establish themselves.

Personally, I aim to keep my seedlings under cover until they reach a thickness of roughly half a pencil. Many gardening authorities will tell you not to plant them out till they are the thickness of a pencil, but this can take a fair amount of time and therefore requires plenty of patience.

I like to plant mine out in spring, around April or May time, so they have plenty of time in the ground to get established and grow before the weather trails off at the end of the summer. While leeks will survive even cold weather, their growth grinds slowly to a halt, so the sooner your leeks are planted out, the bigger they’ll get.

The truth is, leeks are quite easy to grow. The key factor in your success is the actual planting out method. Get this right, and you’ll be enjoying delicious juicy leeks for months to come. Get it wrong and your leeks will barely grow at all and will produce a very disappointing yield.

Transplanting Leeks

Leeks grown with covered protection

As the warmer weather starts to show it’s face, it’s time to begin preparing your leeks for transplanting into their final growing position. Leeks like a sunny and well-drained area, so choose their growing area carefully.

When it comes to planting out leeks there are two factors to be aware of. Firstly, the best bit of a leek is the tender white part of the stem. Leek growers try to maximise the amount of white stem by artificially starving it of sunlight. While it sounds unpleasant, the end result is a far more satisfactory harvest.

There are a number of ways we can accomplish this blanching. Firstly, seedlings can be planted deeply, so that much of their stem remains underground. Secondly, the earth can be built up around them as they grow, further increasing the amount of white stem. Lastly, they can be fitted with “collars” designed to block out the light; one popular option is to use cardboard toilet tubes, carefully placed over the stems to protect them from sunlight (while the leaves are left to freely absorb the sunlight above).

The second factor when growing leeks is not to plant the seedlings too firmly. Packed into tight soil, leeks can sometimes fail to take on their full girth. The end result is very tall yet slim leeks, which don’t offer much in the way of juicy flesh.

Both of these elements can be resolved by adopted one of two popular methods.

The first method for transplanting leeks is to dig a long trench, some 4-6″ of so in depth. The leek seedlings are then deposited along the length of the trench, making sure that the roots are in contact with the earth.

The second method is to use a “dibber” or a broom handle, which is pushed into the soil to create holes some 4″ or so in depth. The leek seedlings are then popped into the holes.

Leeks can be planted reasonably close together; I tend to plant mine around 6″ apart, which gives them plenty of room to grow, while affording me the space to weed between them with a hoe.

Once the seedlings are inserted, they can be watered thoroughly, at which point a small amount of soil should wash down into the hole/trench to cover the sensitive roots. Over the coming weeks, further watering or rain will gently wash more and more soil into the hole, gently filling it up, while at the same time blanching the stems.

Some growers even take things a step further once the holes are filled, and actually start to mound up earth around their leeks, further increasing the proportion of stem that is soft and tender.

Maintaining Leeks

Leeks require minimal ongoing care, apart from keeping an eye on their blanching. Personally I simply keep them weed free, which typically means weeding the patch by hand or using a hoe every week or two during the warmer months. Leeks have quite shallow roots, so try to avoid digging deeply into the soil with a fork or spade; keep your weeding to the surface if possible.

Lastly, I water my leeks thoroughly in hot weather, as dry conditions can significantly slow down growth rates.

Harvesting & Storing Leeks


Leeks can be harvested at almost any size; the question is how long you’re willing to wait before you begin digging them up? At the other end of the scale, leeks do eventually start to develop a “woody stem” over time. This is tough and unpleasant to eat, so if you find a tough centre to your leeks then you’ll want to harvest them as soon as possible to prevent your crop going over.

Typically, though, you can simply harvest a few leeks each week over a period of many months, enjoying a non-stop supply of these delicious vegetables.

Harvesting leeks isn’t quite as simple as merely pulling them up. Healthy leeks will develop an impressive root system, which means you’ll need help to harvest them. The best solution I have found is a garden fork. Simply insert the tines of the fork close to the base of your leek and gently lever it out. The skill is learning how to target just a handful of your leeks, while leaving the others undisturbed in the ground.

If you’re transporting your harvested leeks some distance, then I recommend trimming off most of the green tops, and the thread-like roots, leaving you with primarily the juicy stem. Leeks are a member of the onion family, so the stem is composed of dozens of thin “layers” growing one over the other. Leeks that are still dirty from the soil can either be washed under a tap, or even easier, you can gently peel off the outer layer of skin to reveal moist, clean flesh below.

Leeks will store for a few weeks in your refrigerator, especially if they aren’t allowed to dry out. A sealed plastic container tends to work well. For longer-term storage I like to chop up my leaks and then freeze them in bags. This makes using my leeks simplicity itself, as I simply grab a bag from the freezer and toss it into the pan to defrost and cook through.

All gardeners and vegetable fanatics should learn how to grow leeks. These fantastic vegetables are super-hardy and can provide an ongoing crop for months on end. The only problem is they're not the easiest of crops to grow. This guide, however, shows you exactly what you need to do to grow leeks the right way.

Images c/o rural life amid the burbsLocal Food InitiativeRuth Hartnup.