Last year we lost quite a few onions in storage from a rotting at the top of the bulbs, is there anything we can do to protect this year's crop?

You have described a problem known as ‘Neck rot’

This often starts around harvest time, particularly if wet weather coincides with damage to the onion stems.

Bending over the tops too soon can also result in injury and disease infection.

Take care this year, when bending over the tops, wait until they start to die back naturally.

After lifting, dry the onions off fully by laying them upside down on slatted shelving or mesh in a greenhouse, shed or garage, to ensure there is no excess moisture around the necks.

The tops of my onions are now turning brown, how long should I leave the bulbs before storing them?

As the tops of your onions wither, partly ease the bulbs out of the ground, and leave for a few days. Afterwards, lift the bulbs completely and leave them on the surface of the soil to dry in the sun.

If the weather is wet, lift and lay them directly on to slatted shelving or netting in a warm spot until they are thoroughly dry.

Tie them up into ropes, and hang in a dry, airy place.

Is it better to grow onions from seed or sets?

For really large, exhibition onions it's best to grow the plants from seed.

Advantages; of growing from sets rather than seed:

They give a good yield and require less skill than seed.

They mature quicker.

There is no need to thin them out

They are more reliable under adverse conditions.

Disadvantages: of growing from sets rather than seed: 

They are more likely to bolt

There are less varieties than there are with seed

There is a chance of importing diseases such as white rot or eelworm into your garden

They do not usually store as well.

What are Japanese Onions?

Japanese' varieties are suitable for sowing in Autumn to produce an early crop the following year, but these don't store as well as spring sown onions.

How are onion sets produced?

These are immature bulbs that have had their growth restricted.

They are produced by growing the seed very close together, then harvested in August and stored until late December.

Sometimes the sets are stored at high temperatures ('heat-treated') to reduce the chances of bolting (running to seed prematurely).

What should I look out for when buying sets?

Buy firm, evenly sized sets, about 14 - 20mm (½”-¾”) in diameter.

Beware of bags you can't look into, avoid plastic bags.

Don't buy sets that look as if they have been in a warm shop for some time.

Remove soft, shrivelled or sprouted sets.

On getting them home, space them out in a cool place until you are ready to plant them.