Leeks are easy to grow from seed, and provide a versatile crop that can be steamed, roasted, grilled, steamed, grilled, fried or added to soups and stews. You can even plant leeks in a large container. We asked experienced allotment grower Lee Senior to share his expert advice on growing this delicious member of the onion family. Here are his top tips for successfully growing leeks.
Do you want to try it? Browse our full range of leek seeds.
How to choose the best types of leeks to grow
When choosing the best varieties for your share or patch of vegetables there are two important things to consider. First place. Some leeks are hardier than others and Autumn varieties are generally less hardy.
A second consideration is the length of the growing season you need. With careful planning it is possible to harvest from late September until Easter, giving you a good six months to grow if you like your leeks!
- For a freshly planted autumn variety look no further than Leek ‘Blue Green Autumn Neptune’.
- For winter hardiness and reliability, nothing beats the time-honored Leek ‘Musselburgh’. These varieties grow during the winter period from the end of November to the beginning of March.
- For a late crop, I like the aptly named ‘Northern Lights’ variety. Leek leaves, although not as showy as the original, change color from green to purple as winter progresses. More importantly, it stands well and can be harvested in late April.
Sowing leek seeds indoors
High yielding and rust resistant, ‘Blue Green Autumn Neptune’ is winter hardy
Photo: Leek ‘Blue Green Autumn Neptune’ seed from Suttons
Leeks need a long growing period for the shanks to reach a decent thickness. The time from sowing seeds to planting mature vegetables is 28-32 weeks, depending on the variety.
Over the years, I tend to sow most of the leek seeds indoors in a cool temperature. From the end of February or the beginning of March to sow, the sun can be warm enough to provide sufficient temperatures for reliable germination. Or, if the weather is winter, use a heater or a window warmer to provide the required temperature of 12-18C (54-65F). Germination takes about 14-21 days.
If you are growing show leeks the sowing time is early, from mid-January to early February. These require a long season to grow large. Here are my tips for sowing under cover:
- Fill small pots, modules or deep seed trays with compost or seed compost.
- Sow the seeds thin and shallow to 15mm (half an inch).
- Cover them lightly with compost or perlite and firm gently.
- After germination, grow the seedlings by keeping them cool and out of the spring sun.
- Slow growth of young plants is what you want. Try to keep them hydrated at all times.
- Harden off young plants before transplanting them to their final locations at the end of May.
Sowing leek seeds outdoors
This unusual species turns from green to purple in winter
Photo: Leek ‘Northern Lights’ F1 seed from Suttons
There is no need to sow seeds at the beginning of the year when the soil is still cold and germination will be flexible. Leeks grown outdoors tend to mature a little later than plants started indoors, so a combination of both indoor and outdoor sowing can be helpful.
If the weather is good and you have the space, leeks can be sown directly where you want them to grow when the soil warms in early April. Alternatively, you can start them from a seed bed. Here are my tips for sowing leek seeds outdoors:
- Prepare and raise the soil for good growth.
- Lightly sow the seeds in a seed drill filled with multi-purpose compost to a depth of 15mm (half an inch).
- Water the drill before sowing if the soil is dry.
- Lightly cover the seed drill with good soil, firming it up a bit as you go. I have found that it is worth covering the seed drill with a portable cloche or fleece to aid germination and protect against any cold conditions.
- Germination takes about 18-21 days depending on the weather. This may be longer if it is colder.
- Gradually make the seedlings 20cm (8in) apart and around the size of a pencil. Thinnings can be used for replanting to make new rows. Alternatively they can be used in salads or treated like baby leeks or larger spring onions!
- Leeks can be grown outdoors from seed in early April and then planted in their storage areas. This reduces the need to strengthen seedlings.
Seed tapes are a great way to grow leeks. They are also a great way to get a long growing season as they contain varieties that mature at different times. Suttons 6m leek seed tape contains a number of varieties including ‘Musselburgh’, ‘Neptune’ and ‘Porbella’. The tapes can be used from the beginning to the end of April and they are completely conflict-free. Choose a sunny or shady spot where the soil has been prepared to grow well. Simply make a small groove and drink well before carefully removing the tape and cutting to length. Close the tape lightly and make sure it doesn’t dry.
Planting leeks in their last place
‘Below Zero’ is one of the hardest varieties to grow
Photo: Leek F1 ‘Below Zero’ Seeds from Suttons
The best way to grow leeks is a topic that can divide opinions, and many gardeners have a unique method that works for them. The method you choose may be a little different from your neighbor on your assignment, but that’s okay if it works for you! Here’s how I grow my seedlings outside:
- Choose a sunny spot, although leeks can handle a little shade.
- If growing in more than one row, allow 30cm (12in) between rows.
- Prune young plants when they are about 15-20cms tall (6-8 inches).
- Make the hole 15cm (6 inches) deep with a dibber or your finger.
- Carefully place the plant inside the hole and spread the roots. Most importantly, fill the hole with water so the roots stay.
- Some gardeners fill the holes themselves with soil, like I did, while others leave them to fill in naturally over time. Leave the top 8cms (3 inches) of the leek above the top of the hole. This helps you to get a lot of white flavored white stem that all leek growers are aiming for.
How to care for leeks
This variety has long pale shanks and is resistant to leek rust
Photo: Leek F1 ‘Sprintan’ seed from Suttons
Leeks are not difficult to grow, as long as good gardens are employed. They prefer well-drained, humus-rich soil that contains plenty of decaying organic matter. Try to choose a part of your allotment that hasn’t grown leeks or alliums for several years. If you want tall, green stems, pile soil around each plant in the second half of summer.
Watch out for slugs and snails after planting your leeks. It doesn’t seem to be the first favorite of those weird molluscs, but they’ll take it in wet weather if there’s nothing else around.
Leeks do not like fluctuating humidity levels, especially when newly transplanted. And they don’t like the cold spring weather and any checks on their growth. This can encourage plants to bind which is one of the most common problems. If the plants start to bind, the trick is to remove any flower spikes early while they are short and still growing. If you don’t, the plants will become wood. If you catch and remove the flower spikes early enough, some leeks can be used as normal. (It is important to note that the young flowers are edible and have a pleasant aroma.)
Rust is common on leeks, and wherever I’ve grown them it seems to follow me! This so-called ‘rust’ is actually a fungus. Those orange spots are worse if the leeks are grown too close together in wet, humid conditions. Although common on leeks and alliums, rust is usually harmless but unsightly. Try and choose resistant varieties when possible.
How to harvest and store leeks
These three types of leeks offer a long growing season for use in the kitchen
Photo: Leek Seed Tape from Suttons
Leeks can be well dug up using a fork under the plant. Simply loosen the soil, apply the roots and shake off the excess soil. If you have fertile or free-draining soil, it can also be harvested by hand by gently pulling and twisting. It must be said that sometimes it can break too, if you draw too fast, so use this method with caution! I would not recommend it for heavy soil.
Since leeks are a winter crop, there may be times when you want to harvest from frozen ground. If this happens, I may still dig carefully using a spade in my experience. But if a long and heavy frost is predicted, you can dig a few in advance and store them in a container of soil in the garage to use in a few days. The frost itself does not harm the plants, in fact, it could be argued that it brings out the flavor.
Leeks can be stored in the refrigerator for several weeks, although they will definitely begin to soften over time.
We hope we’ve inspired you to try growing your own leeks from seed. Find out more of Lee’s practical, hands-on, gardening advice on his monthly share pages.
