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Leeks are hardy enough to grow outdoors through winter in most regions. You can make the harvest period last from autumn right through to spring by carefully selecting a mix of varieties. Look out for varieties described as ‘rust resistant’ if this fungal disease is a problem in your area.
Start sowing under cover from late winter. Our Garden Planner provides personalized sowing, planting, and harvesting times for crops in your location, using data from your nearest weather station.
Sieve potting soil into pots or trays. Gently tamp it down. Sow the seeds about an inch apart (or sow two seeds per cell in a plug tray). Sieve more potting soil over them to cover, and then water them. Keep the potting soil moist but not too wet as the seeds germinate and grow on.
Place early sowings on a sunny indoor windowsill or in a greenhouse. As they grow, you can separate the seedlings into individual pots if you wish.
Transplant your leeks into well-dug soil when they are 6 to 8 inches tall. Make sure to harden them off first by leaving them outside for increasingly longer periods over a week or two.
Dig holes that are nearly as deep as the leek seedlings are high using a purpose-made tool or the handle-end of a short garden tool such as a trowel. The holes should be spaced 6 inches apart, with a foot between rows. If you’re planting in blocks, space them 7 inches apart each way.
Carefully remove the leeks from their pots and (if they haven’t already been separated) and tease the roots apart. Place the seedlings into the holes, making sure the roots reach right down to the bottom. Fill the holes with water and leave to drain. Do not fill in the holes — the soil will naturally fall back in with time, blanching the stems while allowing them to swell.
Grow fast-growing salads in between your newly planted leeks to make the most of your space, but make sure to harvest them by midsummer, when the leeks will need the space to grow well. Water the plants in very dry weather and hand-weed or hoe the ground between them regularly.
For exceptionally long, white stems, draw the soil up around the leeks two to three weeks before you want to harvest them to exclude light. Alternatively, tie cardboard tubes around the stems.
Harvest your leeks as soon as they’re big enough. Lever a leek out with a fork while pulling up on the leaves. In very cold regions you may wish to dig up your leeks before the soil freezes solid, but in many areas hardy varieties can be left in the ground and dug up as needed.
Learn more about growing leeks in this video.
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