Agriculture Reference
In-Depth Information
Preparation
Onions prefer rich, light soil, although they will cope with any adequately
drained soil provided that there is a reasonable tilth for their shallow roots. They
also like quite a bit of nitrogen, so top dress the bed with manure or compost in
May. So long as you do some top watering and there are plenty of worms around,
the soil should be ready by July. If not, or if you have to add the organic matter
later, work it into the soil with a garden fork, rake the bed over, tamp it down
with the back of the rake and top water it well for at least two weeks before
planting.
Sowing sets
Plant at 10cm intervals in rows (for easy weeding) 30cm apart, with the tips just
above the soil surface (make sure the rooted end is at the bottom). If you plan to
lift the bulbs earlier than late May, you can sow them as little as 5cm apart.
Sowing seeds
Sow two seeds per small module, and remove the weaker seedling if both come
up. The seedlings are delicate and slow to get started, so delay moving them to
the soil beds until they are 10cm tall. Space them as for sets, but watch out for
slugs until they are established.
Growing
Onions compete poorly for light, so keep them thoroughly weed-free. If they dry
out it can affect both their flavour and the eventual yield; a mulch of grass clip-
pings or other organic matter can be used (but keep an eye out for woodlice and
slugs) to suppress weeds and reduce moisture loss from the soil. Keep them well
watered until they show signs of ripening (when the tops are beginning to yellow)
and then reduce irrigation. Any onions with a hard flower stem should be har-
vested immediately, as the bulbs will not grow any larger and will not store well.
Harvesting and storage
For fully mature onions, leave the plants until the leaves start to turn yellow and
fall over, but provided that you don't mind smaller bulbs, you can trigger early
ripening by partially easing them out of the ground with a garden fork, folding
the necks over firmly, and reducing watering straight away. After a week or two
like this the onions will be sweet enough to cook with, but if you intend to store
them they will need to 'cure'. Lift the plants right out of the ground and gently tap
away the soil from the roots. Then move them to a sunny spot with good air circula-
tion; a suspended shelf in your tunnel is ideal. After a couple of days any remain-
ing earth around the roots will have dried and can be rubbed off by hand. Curing
time depends on temperature and humidity but is usually two or three weeks. To
see if they are ready, roll the neck of one or two of the larger specimens firmly
between finger and thumb. They should be dry and papery with no hint of
squishiness.
