Growing Onions from Sets

The Onion Sets that you buy are immature bulbs specially grown for planting. They have an advantage over seed in that they are quick maturing and slightly less prone to disease but they can have a tendency to 'bolt' or go to seed. Some of the modern varieties of sets are now heat treated to destroy the internal flower bud, which stops this bolting. Shallot sets are grown exactly the same as Onion sets. They do not grow any bigger than when planted but multiply and form a cluster of 8 - 10 similar size bulbs. They are milder in taste than Onions.

Unlike Onions grown from seed, they are quite happy in any sort of soil but will benefit from organic matter in the soil. Prepare the bed by digging over and raking flat, incorporating a general fertiliser.

Plant the sets in March or April in rows. Space them 4" apart with 9" between the rows. Plant them by just pushing into the soft earth and pulling the earth back around them. Leave just the tip showing.

Sometimes birds can be a problem and pull the sets out. If this happens, replant the sets and cover with a net.

Keep weed free and only water if the weather is extremely dry. Sometimes a thicker flower stem will grow, if this happens break it off.

When the bulb is mature the foliage will droop and dry off. Leave a further fortnight and the lift the bulb using a fork. Do this on a dry day. Place the onions on a tray (split up Shallot sets) and leave in a dry sunny place to ripen. Sort the onions and remove any that are damaged or have thick necks. Use these first, the good ones can then be stored by stringing together (see instructions) or putting in net sacks for use over the winter.

Japanese Onion sets are planted in the autumn and over-wintered. These provide a slightly earlier crop in the summer.

Onions can suffer from many of the general garden pests and diseases including Aphids, Onion fly, Onion Eelworm, neck rot, white rot and storage rot. (See relevant Pests or Diseases sections).

© copyright 1999, P. A. Owen