Preparing the soil
Leeks prefer a fertile soil, dig in well rotted manure to raise nutrient levels up. Choose a sunny site, though they can tolerate some light shade. As they are a long crop and can be left in the soil through winter and picked when needed, they need soil that is free draining and will not get waterlogged in the winter. This can lead to rotting and other soil borne diseases.
If planting in spring then add a sprinkling of fertilser before preparing to plant.
Planting
Plant Leeks through Spring from March to June, then again for later winter/early spring varieties in September and October.
Leek Seedlings - Plant leek seedling quite deep in a hole approx 15cm deep and 15cm apart, with 30cm between the rows. Drop the seedling in the hole and then fill will water, this will settle the soil around the seedling and water the plant at the same time.
Leek Garden Ready Plugs - Make a hole the same size as the plug but a little deeper so some of the green stem is in the soil. Firm back round or just water in and let the soil settle back to fill the hole. Plant each plug 15cm apart, with 30cm between the rows.
Growing
Ensure plants have enough water through the Summer so they have even, steady growth. If you want extra white long stems, then you can earth up the soil around the stem as it grows, similar to earthing up potatoes. This ‘Blanches’ the stem as the darkness keeps the stem white and softer.
Mulching in the summer will help with moisture retention and keeping weeds from germinating. Remove any weeds that do get through, as leeks have a lot of open soil around them, weeds can become troublesome quickly.
Cover with fine horticultural fleece to deter insects especially allium leaf minor, leek moth and onion fly. Leeks can be prone to Leek rust which can affect leaves and lead to secondary infections. Choose to grow rust resistant varieties. Remove any leaves as soon as you see any symptoms appear, but dont put them in the compost heap.
Leeks can sometimes bolt, where they go to flower too early. This can be caused by being too dry or stressful growing conditions. Remove this as soon as you see it and pick the leek soon after.
Harvesting
If you want to grow baby leeks, these can not only be spaced closer but harvested quicker. Larger leeks take approx 4-5 months to mature but can be left in the ground through winter and early spring and lifted as required. You can pick Leeks alternately, giving the remainder more room to grow on. Lift using a fork under the roots and gently pull up. Harvest when the stem are even in width, Leeks left too long will start to swell at the base.
Give the leeks a good wash before taking them into the kitchen, removing any soil or splash on the leaves.