Do you know your onions?

Most vegetable sowing has to be timed to coincide with the arrival of spring, otherwise the seeds just sit there and rot. But onion sets can be planted in the weeks approaching spring and they are often the preamble to serious sowing.

I always choose growing onions and shallots from sets - those little onion bulbs you see in packets - simply because it's much easier than growing them from seed.

There are two types of onion set. Firstly, those that are simply grown and stored. These are available during the early part of the year. Heat-treated onion sets are available from mid-March onwards and they are much less likely to bolt or run to seed. Good varieties of round golden onion include Shakespeare, Sturon, Hercules and Setton. The latter two are both improved hybrids of Sturon.

But it is the hotter red onions that gardeners are going for. Red Baron can't be beaten. But red onions are trickier to grow and more likely to bolt in dry springs. Some gardeners raise their sets in old plastic drinking beakers (with holes made in the bottom) so that they form a root ball before being planting out.

I also grow some shallots for the kitchen. Their mild flavour brings out the best in chicken and pork. As a young gardener I was always told to plant them on the shortest day and harvest them on the longest. A good tale, but I'm afraid they go in during March and get harvested in August.

Like all bulbous plants, onions and shallots prefer well-drained soil. But both are shallow-rooted and they can't dig deep for nourishment, so your soil should be rich and fertile. For this reason onions are often sown on ground that's been enriched in the previous weeks or months. Ideally, the ground should be rich in potash too. Gardeners often used to spread their wood ash on the onion patch.

Rotating your onions, moving them to a different place every year, is vital too. It helps to prevent disease and onions are prone to rot, principally white rot and neck rot.

Birds love to pull onion sets out, so snip off any ragged ends at the top of each bulb before planting in an open sunny position. Just leave the minutest tip showing. I space each bulb 6in apart, with 12in between the rows. The ideal growing pattern for onions is a cool, damp spring (to promote leafy development) followed by a hot summer to ripen the bulb.

As the bulb matures, the foliage begins to wither and brown. Loosen the roots with a fork until the onion lays on the soil surface and then lift them and place them on a raised wire netting frame. Once the bulbs are fully dry, they can be stored in a sack, an open tray or strung up into a string. Make a loop with a length of strong twine, measuring 4ft. Tie the loose ends together and thread each onion stem through the loop, starting at the bottom and just keep going upwards.

Supplier: A good range of varieties are available from Thompson & Morgan. Call 01473 688 821, or click on www.thompson- morgan.com