Leeks

Overview

Leeks   Allium ampeloprasum porrum        Rotation group - Roots

Leeks are one of the important Winter vegetables they are available from November right through until the following March.  They require a very long growing season it is almost nine months from first sowing the seed to harvesting the first leeks. All of the waiting is well worth it because they have a sweet, mild taste and smooth texture that belies their rough and ready reputation.

Varieties to choose (sold by Kings Seeds): -

• Musselburgh - strong growing habit with thick stems. Very winter hardy, ready from December onwards
• Carentan (organic seed) - large thick stems with blue green foliage
• Giant Winter (AGM) - excellent late variety with fine, long, white stems which will stand in the ground for a longtime

How to grow

Sow

Leeks are raised from seed.  If you can provide a temperature 55F/13C and the protection of a greenhouse the seed can be sown as early as January in pots or trays filled with fresh compost. However, there is always the risk when starting the leeks off too soon that they suffer a check to their growth at some stage causing the plants to bolt later in the season. It is better to wait until late February/ March before sowing the seed. The seed can be sown outdoors in a well prepared seed bed, but with the potential problem of attack from leek moth and leek fly it is safer to start the seed off in trays or pots filled with fresh seed compost. Just as the seedlings are beginning to uncurl and straighten up is the ideal time to prick them out into trays or boxes filled with fresh potting compost. Space them out leaving 2ins/5cms between each seedling. Grow them on in until they are at least 9”/20cms tall before they are ready for transplanting. This is carried out sometime during May try to wait for cool and cloudy weather conditions to prevent putting the young transplants under too much stress.

Growing on

It is important that the leek bed is well prepared beforehand. The soil needs to be in lightly firmed but still soft underneath. This is because the easiest way to form a tender white stem (blanching) is to transplant the young leek plants so that the base of the leek is at least 9ins/20cms below the surface of the soil. Young leeks are planted with a dibber these are usually made from a broken spade or fork handle. It is important to use a dibber with a blunt end if it is too pointed it will leave the roots of the plants hanging in the air. It is better to make all of the holes along the row first and then drop the leek plants in one operation. If the surface of the soil is too dry and keeps falling into the hole water along the line of the row first to bind the soil together. As the dibber is pushed into the soil it needs to be twisted from around to smear the walls of the hole which prevents them from collapsing. Thoroughly water the tray or box containing the leek transplants before gently tipping all of them out of the tray or box. Carefully separate the individual plants and wash the compost off the roots. The next job is to cut down the roots leaving them  ½ inch/12mm long this doesn’t harm them and it makes them easier to drop into the hole. The other part of the operation is to reduce the foliage by about 50% this helps to overcome the problem of water loss through the leaves before the roots begin to regrow. It also helps to make it more difficult for the birds to pull the young leeks out of the hole. The last job is to water each leek plant in. Use a watering can with the rose off and fill each hole containing a plant right up to the top. This will help to puddle the roots in and provide enough moisture during this delicate period in the leeks development.

Aftercare

Inspect the leek bed regularly over the two weeks after transplanting and if any plants have been pulled up and left on the surface of the soil pop them back in the hole and water in as already described. If the plants have been lying around and have been baked in the sun or shrivelled by the wind replace them with a substitute plant held back from the initial transplanting operation.

Over the weeks following transplanting the hole will gradually fill up with soil but it won’t affect the development of the leek plants. Hoe regularly between the rows of plants and water during long dry spells.  An occasional application of a foliar feed of liquid seaweed will help to prevent the plants from becoming stressed especially during a prolonged dry spell.

The leek plants will be fully grown by November but there’s no need to rush to dig them up. Leeks can remain in the soil until they are required for lifting. The cold winter weather will hold them back preventing any further growth. The only thing to take into consideration is the harvesting season of the cultivar(s) being grown. The early types will be a little less hardy than the later types so they must be used first. The later, hardier leeks can be left alone until the New Year and they will be available to use well into March.

How to Harvest

Leeks are dirty crop to dig up there always seems to be soil and water everywhere it is the sort of jobs that is best done wearing waterproof trousers. It is worth taking the time to prepare a washing area and to have an old knife or secateurs ready to trim the tops and roots. The soil clings to the roots and has to be washed off before trimming them back to about 1ins/2.5cms from the base of the leek.  The foliage of the leek is cut off about 2ins/5cms above the top of the blanched stem. The leek may need a final wash down before taking to the kitchen because soil gets trapped in the folds of the leaves.

If the weather forecast is predicting a long cold or wet spell it is worth digging up enough leek plants to cover the period. They can be replanted in a large pot or bucket filled with old potting compost / garden soil or in a small trench in a sheltered postion alongside a building. They can be kept in a cool garage, cellar or shed for short period.

Issues

Leek moth and leek miner are the two major pests. See our Pests and Diseases page for more information.