Leeks, which are famous as the Welsh national emblem, are related to the onion but easier to grow. They have flat overlapping leaves forming an elongated cylindrical bulb which together with the leaf base, is eaten as a vegetable. They generally mature in autumn/winter and hence are a tasty addition to any winter stew or soup such as your classic Leek and Potato.
As with other plants there are three main varieties – early, mid season and late. So decide which ones you want to have or get all three. I would just go for one variety as I want as many different vegetables growing in my patch as possible. It depends how many leeks your household gets through...
SOW SEEDS IN GREENHOUSE/ON WINDOWSILL: February to April
SOW SEEDS DIRECTLY OUTDOORS: March to April
TRANSPLANT OUTDOORS: May to July
DEPTH TO PLANT SEEDS: ½” (2cm)
DISTANCE BETWEEN ROWS: 12” (30cm)
DISTANCE BETWEEN PLANTS: 6” (15cm)
Leeks are tolerant of a wide variety of soil types but prefer firm, well drained soil. A safe bet is to dig well rotted garden compost into your soil. Freshly manured soil is not suitable. There will be too much leaf growth and the resulting leeks will be coarse, tough and no good for eating.
When to Plant
There are 3 sowing dates for leeks – if planting from seed they should be sown in Rootrainers before planting out
|Summer and Autumn (Hannibal)
|Autumn & Winter(Blue-green winter, Northern lights)
|Mid March||Mid May|
|Late Winter (Blue Solaise)
|Early May||Early June|
It is usual to start the seeds off in containers or a seedbed before moving them to their final position once they are established. This is because sowing them directly into their final position takes up a lot of space which could be being used for fast growing crops such as lettuce. Leeks are perfectly happy to start off in the greenhouse or windowsill and move when your salads are done.
Growing from seed is easy and germination rates are high. Sow your seeds into Rootrainers or small 3” (8cm) pots.Germination should take from 14-21 days.
Start thinning the seedlings out straight away. Thin to about 2" (5cm) the first time as some of the plants may die, and then thin again when everything seems to be going well, so that the plants are about 4" (10 cm) apart.
If you don't want to plant seeds you could also let someone else do the work and buy established seedlings and plant out as the weather permits.
When the leeks are about 8" (20cm) tall, plant them into their final positions. If possible plant when the weather is showery, if not then water them well. Keep watering well until they are really established.
To ensure you get lovely blanched stems make a deep hole around 6" (15cm) to plant the leek. Fill in with an inch or two of soil and allow the remainder of the hole to fill up with soil as it is washed in with watering. This will ensure some white stem on your leek which many think is enough (both white and green parts of the leek are edible). If you want more white and less green though, see the section below on Blanching, for how to use collars.
When choosing the site to sow leeks make sure you consider that you might want to leave them in the ground to be dug as required during the winter months, and you could leave them in the ground for a year or more.
It is not advisable to grow leeks in the same place year after year as there will be an increased risk of pests and diseases such as Leek Rust.
In crop rotation, leeks follow lettuce, cabbage or peas. Many people leave planting their leeks until immediately after lifting early potatoes. However, do not plant them where the potatoes were as the soil will be too loose and disturbed and leeks do best on a firm soil.
Leeks need food and will benefit from a sprinkle of something like a seaweed feed around the roots. This will increase the thickness of the leeks. Don’t feed overwintering leeks after August.
The leeks you buy in the supermarket will have long white stems. To increase the length of white stem in your home grown leek, blanch the stem by gently drawing up dry soil around the stem in stages. Start this process in August.
If you have your leeks growing in a trench, gradually fill the trench in with soil to the bottom of the lowest leaves each time until the plants have finished growing, which will probably be around mid to late autumn. You are aiming for 4-6" (10-15 cm) of blanched stems. Use dry, fine soil to do this as wet soil will cause rot to set in and lumpy soil wont keep out the light properly.
If your leeks are growing in a flat bed or container, push the soil up around the plants increasing the soil depth by about 2" (5 cm) each time. You can keep the stems free of soil by using collars. Secure them around the leeks leaving around 5" (12.5cm) of leaf showing.
Get your recycling hat on for this bit as many materials are suitable to make a collars. For instance, sawn lengths of plastic piping, the middle of toilet rolls and wrapping paper, or brown paper tied up with string or rubber bands. Whatever type of collar you decide on the minimum diameter should be 3" (7.5 cm) and 12-15" (30-37.5cm) long. Attach the collars before carrying out the earthing-up process. The collar will keep the light out and the soil will stop it blowing away in the wind. As the plants grow, draw up more and more soil adding another collar if needed.
This will increase the amount of the plant that is edible and improve the flavour. Keep the soil from falling between the leaves otherwise you will have a lot of cleaning to do or risk gritty stew!
Harvest your leeks by lifting gently with a fork, either as pencil thin baby leeks or as fully grown 3” (8cm) diameter ones.
If you want to eat them then do not let your leeks flower as the leek turns into a woody stem once the plant flowers and is too tough to eat. Leek flowers are a very decorative addition to the garden though so you might want to let some of them flower as they will produce seeds that you can happily collect to use the following year.
Leeks will stay fresh for 1 to 2 weeks if stored in a cool place. Once harvested they are delicious in soups or stews or try them in a white sauce covered in cheese and grilled. A perfect side dish for your Sunday roast and a lovely vegetarian lunch in its own right..