AUTUMN-PLANTED onions are easy to cultivate, give a good harvest and keep your soil productive in winter – so why don’t more gardeners grow them?
It’s probably because many people shut up shop in October. That’s a shame, because once planted, sets are a doddle to look after – leave them to it.
A set is an immature onion, easier to grow and less prone to disease, but more prone to bolting (setting seed if weather conditions are bad) – buy heat-treated varieties to prevent this.
If your soil is very heavy and prone to waterlogging, it’s best to plant onions in spring, or grow in raised beds.
Choose an open, sunny site and well-drained, non-acidic soil (below pH6.5). If you do have acid soil, apply lime in autumn and winter.
Enrich the soil with plenty of organic matter, but avoid using fresh manure.
When planting, apply 35g per sq m (1oz per sq yd) of Growmore or specialist onion fertiliser. If you don’t have any organic matter (compost, etc), double the amount.
Place each set with the growing tip peeking out - cover with netting if you have a problem with birds pulling them out of the ground. Firm in and water. Don’t plant if the ground is waterlogged or frozen.
Apply a nitrogen-rich fertiliser such as sulphate of ammonia or dry poultry manure at the rate of 35g per sq m (1oz per sq yd) in late winter to boost growth and suppress bolting.
Plants must be growing strongly by late spring as the lengthening days trigger the formation of bulbs.
As the foliage casts little shade, onions can be overtaken by weeds. Don’t use a hoe, as this can damage the bulbs - you’ll have to hand weed, I’m afraid.
Water every 14 days during dry spells, but avoid overhead irrigation that encourages fungal diseases. Bulbs should be ready June-July.
Planting time (sets): Sept-Nov
Harvesting time: midsummer
Planting distance: 5-10cm (2-4ins) apart
Aspect and soil: Full sun, well-drained soil, avoid acid soils
Recommended varieties: Red Cross, Senshyu, Shakespeare, Electric, T&M’s first Early, Tornado, Radar, Troy.