Leeks are ready to transplant in June when they are about 20cm (8in) high and the thickness of a pencil. Water well the day before lifting and transplanting. Prepare the plants by trimming off the root tips.
Make 15cm (6in) deep holes, 15cm (6in) apart in rows 30cm (12in) apart and drop a plant into each hole. Fill the hole with water to settle the roots. You don’t need to backfill the hole with soil, just let the water settle the soil around the roots. If you have a lot of plants, try dropping two or three into each planting hole. You'll get smaller leeks but the overall yield should be the same.
To increase the length of white stem it can be blanched by gently drawing up dry soil around the stem in stages, but try not to allow soil to fall between the leaves.
Water during long, dry spells and weed regularly.
Onion white rot: A soil-borne fungus that can cause yellowing and wilting of the foliage above ground, while rotting the roots and invading the bulb beneath the soil. A white fluffy fungus appears on the base of the bulb and later becomes covered in small, round black structures.
Remedy: There is no chemical cure for onion white rot when it is the soil. It is important to avoid introduction to previously clean sites. It is transported in contaminated soil, for example on tools or on muddy footwear. Take particular care in areas where cross contamination can occur easily, for example on allotments.
More info on Onion white rot
Leek rust: This is a fungal disease causing bright yellow spots on the leaves. It is often worse in long, wet spells.
Remedy: Mild attacks of rust won’t harm the plant, but serious infections may cause leaves to shrivel and affect yield. There is no control for rust once you have the infection. Make sure you don’t crowd plants, as this increases humidity and increases the likelihood of infection. Dispose of any badly affected plant material, and don’t grow garlic, leeks or onions in the same spot for three years.
More info on Leek rust
Leek moth: This is a relatively new pest of leeks and onions and thought to be mainly concentrated around the south-east coast of the UK, although it has been found further inland and north. Caterpillars tunnel into the leaves, causing whitish-brown patches to develop on leaves. In severe cases, leaves may turn yellow and rotting occurs within them.
Remedy: Once you see the damage, there is nothing you can do to control it. Remove and destroy infected plants. When planting out, cover leeks with horticultural fleece (like Enviromesh) to prevent adult moths from laying eggs.
More info on Leek moth
Start lifting when the leeks are still quite small to ensure a long harvest period. Gently lift from the soil using a fork.
Leeks can remain in the ground through the winter until they are needed.
Anthony Worrall Thompson includes leeks in his Root vegetable gratin Dauphinoise
Nigel Slater adds leeks to his Artichoke soup with ginger and walnuts
‘Carlton’ AGM: This is a top choice with seed that germinates and grows quickly. The stems are ready to harvest September to November.
‘Pancho’ AGM: An early maturing cultivar with long, crisp white stems and good rust resistance.
‘Apollo’ AGM: A mid-season cultivar, ready to harvest in about December with blue-green leaves and good rust resistance.
‘Toledo’ AGM: This leek produces long stems with dark blue leaves and is a late season cultivar, ready to harvest late November to late February.