Onion

Growing Guide

Early sowings (December to March) can be made indoors in pots or seed trays , sow seed on the surface of seed sowing compost and lightly cover with a sprinkling or vermiculite or compost and place in a propagator or polythene bag until germination. Indoor sown seedlings can be pricked out into individual pots before moving to a cold frame in April to harden off before planting outside 15cm apart.

Outdoor sowings can be made in April, sow seed thinly in shallow drills 1.5cm deep, with rows spaced 30cm apart. Outdoor sowings can be thinned gradually until plants are 15cm apart, then leave to mature as smaller bulbs for storing. Pull the thinning’s carefully and remove from the site to avoid attracting onion fly. Thinning’s can be used as salad onions.

Water in prolonged dry spells every 14 days, and give an occasional feed with a general liquid fertiliser. But stop watering and feeding once the onions have swollen in mid-summer. Watering spring-planted crops after mid-summer can mean they store less successfully. Try to avoid overhead watering, as this can encourage fungal diseases.

TOP TIPS

Although usually grown from sets, onions can be grown from seed, sown either indoors or outside. Seed is cheaper to buy, but slower to grow and the

seedlings need more careful attention, however seed-grown plants can be less susceptible to bolting (flowering). To ensure a good crop, seed-raised plants must be growing strongly by late spring, as the lengthening days trigger the formation of bulbs – the more leaves plants have at this time, the better the bulb will be.

Yellowing and toppling of the foliage is a sign that the crop is reaching maturity. Once the yellowing begins some gardeners gently fold down the stem, the theory being that this encourages the bulbs to swell even more - we've tested this and didn't see a noticeable difference, but nor did it harm the plants. Harvest before the foliage dies down completely. Carefully lift the bulbs with fork, taking care not to damage or bruise them, as this could cause them to rot in storage. Use any damaged onions straight away.