Leek plants are exceptionally hardy, and they are generally trouble-free, the best of all they can provide beautiful long stems from autumn right the way through to spring at a time when other harvests are thin on the ground.
Actually Leeks are very hardy vegetables, which in most regions will safely sit through frost and snow to be lifted as needed. You can prolong the harvest period by selecting a combine of varieties. Early season leeks are less hardy but will be ready for autumn, while mid and late season leeks will give you smooth stems for winter and spring.
Make sure you grow leeks in a sunny, open position in well-dug soil that has plenty organic matter. The fungal disease rust can be a small problem from summer onwards, make sure you look out for varieties described as ‘rust resistant’ and also leave enough space between plants for good air movement.
How to Sow Leeks
The earliest varieties of leeks can be sown under cover from late winter, with others following on from mid spring. Actually leeks are usually sown in pots or trays of potting soil and later transplanted into their final position when they’re actually big enough.
Sowing leeks is very easy. You can start by sieving potting soil into the pots or trays. Gently tamp the potting soil down, and then sow the leek seeds very thinly so they can fall about an inch (2-3cm) apart. You can also sow 2 leek seeds per cell in a plug tray. Then cover them over with a thin layer of more potting soil, and water them. Make sure you keep the potting soil moist as the leek seeds germinate and as the seedlings grow on.
Early sowings should be placed on a sunny indoor windowsill or into a greenhouse where the warmth can encourage quicker growth. As the seedlings grow you can if you wish separate them out and pot them into individual pots.
How to Transplant Leeks
Before transplanting your young leeks outdoor make sure you’ve acclimatized the plant to outdoor conditions by leaving them outside for increasingly longer periods over the course of 1 to 2 weeks. They’re ready to transplant when they are 6 to 8 inches tall.
How to Plant out leek seedlings
Start by ‘dibbing’ (poking) holes that are about the same height as the leek seedlings’ stems into a well-dug soil. Actually you can use a purpose-made dibber for this, or improvise with a cut-down handle from an old broken spade or fork, or you can even use the handle-end of a hand tool such as a trowel. Make one hole for each leek plant. The holes should be about 6 inches (15cm) apart, with about a foot (30cm) left between rows, or if you’re planting in blocks space them 7 inches (20cm) apart each way.
Now carefully remove the leeks plant from their pots and, if they haven’t already been potted on, tease the roots apart. Place the seedlings into the holes. It’s very important that the roots reach right down to the bottom of the hole, so if necessary, help them along – you may need to trim them to get them in if they’re very long.
With your leeks in position, fill the holes to the brim with water and leave to drain. Make sure you don’t fill in the holes. The soil will naturally fall back in with time, allowing the shanks (stems) to swell easily.
How to Care for Leeks
If you want to maximize space you can grow fast-growing salad leaves in between your newly planted leeks while you wait for them to establish. Salad crops are shallow-rooted so they won’t compete with the deeply-planted leeks. By midsummer the leeks will need all available space to encourage high light levels and good air circulation.
Easy-care leeks need very little attention. Water the leek plants in very dry weather and also keep the ground between the leeks weed-free by hand weeding or hoeing weekly.
If you want really long, white stems, you can ‘blanch’ your leeks 2 to 3 weeks before you want to harvest them. Simply draw the soil up around the shanks to exclude light, or tie cardboard tubes around the stems.
How to Harvest Leeks
Leeks can actually be harvested as soon as they’ve reached the desired size. Slip a fork underneath the plant to lever it out, while pulling up on the leaves. Trim the roots and any damaged leaves onto the compost heap then wash away the soil ready for the kitchen. Hardy varieties of leeks may be dug up as needed over the winter, though in very cold areas you may want to dig them up before the ground freezes solid.