Page 19 - ALG Issue 1 2025

VEGETABLES
Preparing the soil
Choose a warm, sunny spot in well-drained soil, where you haven’t grown leeks or other members of the onion family for several years.Weed the ground thoroughly. For a bumper crop, improve your soil
by digging in two buckets of well-rotted manure per square metre/yard, especially if you have lighter, free-draining soil. Leeks don’t do well in very acidic soil (below a PH of 6), so, if necessary, reduce acidity by adding lime in autumn or winter.
Although leeks are best suited to growing in open ground or raised beds, you could plant several in a large, deep container filled with multi-purpose compost (preferably peat free). Leeks for exhibition are almost always grown in raised beds/trenches, containers and usually under cover.
To get a head start and an earlier harvest, you can start leeks off indoors from late winter onwards on a warm windowsill or in a greenhouse, at temperatures above 7°C (45°F).and transplanted outdoors after about eight weeks, when 20cm (8in) tall, after the last frost.This is also a useful option if you don’t have enough space outdoors in spring.
Sowing outdoors
The prime sowing months for leeks are March and April, either temporarily in a seedbed or straight into their final position if you have space available.You can also sow later-cropping varieties in May and June, for harvesting in winter and spring, as well as fast-growing varieties for harvesting as baby leeks.
Once leeks are growing strongly in their final position, weed them regularly, water during dry spells, and ‘earth them up’.This
simply means drawing up dry soil around the plants, to blanch them and produce the characteristic long white shank. Do this several times as they grow but try not to let soil get in between the leaves. Another method is to prepare a hole using a dibber, drop the seedling in and water.
After that, you should only need to water during dry weather, repeating every couple of weeks until it rains. Leeks growing in containers will need regular watering across the season, as the compost will dry out much more quickly.Try to avoid overhead watering, as this can encourage fungal diseases such as leek rust. Apply a thick layer of mulch, such as well-rotted manure or garden compost, around leek plants
to help hold moisture in the soil.This also helps to deter weed germination.
Weed regularly so young leeks don’t have to compete for light, water and nutrients. Leek foliage casts little shade, so weeds grow readily around them and can soon swamp them, which will hinder their growth.
Potential problems
Leeks are relatively trouble free, although they can be affected by several fungal diseases, including leek rust and onion white rot, especially in damp conditions.
Avoid planting leeks in soil that gets
waterlogged. Potential pests include leek moth, onion fly and allium leaf miner – if these are a problem, then grow leeks under insect-proof mesh. Slugs and snails may eat seedlings and young foliage. Flowering (bolting) can be caused by low temperatures in spring, so cover early sowings with a cloche or fleece. As soon as you spot a developing flower stalk, remove it, as it can turn the centre of the leek woody. If removed while still in tight bud, they are delicious lightly cooked.
Propagation
Vegetative propagation is used by exhibitors to maintain a particular strain of leek.These strains have been hybridised and perfected by expert amateurs over many years. By vegetative propagation, the strain is kept true to the original. It is rather like taking a cutting from a plant and growing it on.The cutting will be a carbon copy of the parent. When growing for show, this has obvious advantages to the exhibitor for as well as having all the good qualities of the parent plant, it also becomes much easier to match the leeks for uniformity. Space does not permit me to expand on growing leeks for exhibition, perhaps another article!
David Allison, NAS Horticultural Expert Allotment and Leisure Gardener | Issue 1 2025 | 19