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Feature imageGame, set and match

Growing onions from seed can be demanding. Sets can offer an easier option and Andrew Tokely explains how to get the best results from them

Onion set factfile


Onions

• Onion sets are little bulbs that were sown from seed by professional producers and harvested when immature. They are then stored for later replanting by us.

• The sets are sold either treated or untreated; untreated sets are available from January until April, whereas heat treated sets are available from mid-March onwards.

• Heat-treated varieties are usually slightly more expensive because they have been specially prepared over a period of 20 weeks. This heat treatment reduces the risk of premature bolting (running
to seed).

• The skins of heat-treated sets are usually a darker brown, and have a lower moisture content. They are slightly slower to start into growth than an untreated set.

• Heat-treated sets are delivered later than untreated sets to allow time for the treatment, but are worth the wait and the little extra you may pay as the onions you harvest will be of a far better quality.

• During late July through to late September autumn onion sets are sold in garden centres and via mail order and these are sometimes called Japanese onions. These sets are autumn planted and will overwinter on the vegetable plot to provide you with fresh bulbs to harvest from June onwards, usually at a time when your stored onions are coming to an end.


Onions
Growing onions from seed sown direct in the plot is often unpredictable as germination can be erratic during unsettled weather conditions. That’s why many vegetable growers decide to grow their onions from sets (small bulbs).
I would always advise new gardeners to master the art of growing onions from sets before attempting to grow them from seed.
When growing your crop from sets you are almost guaranteed a good harvest and these small bulbs can be planted at various spacings to provide the size of bulb you want (in our kitchen, there are complaints if the onions selected are too large).
There is another big advantage to growing onions from sets; there are varieties that are suitable for planting in the spring and others for planting in the autumn, providing you with a full season of onions to harvest fresh, or from store.

When to plant

September – early November
Autumn planted onion sets are traditionally planted direct outside in early September. Recent trials and warmer autumns have resulted in a change of planting time by commercial onion growers and many gardeners are now also following this planting pattern. It has been discovered that the best time to plant autumn sets is in late September to mid October, as they are less likely to bolt.
If you live in the southern half of the country you could even delay planting until early November and you will still get a reasonable harvest of slightly smaller bulbs.

Mid-March to mid-April
Providing the soil conditions allow, untreated onion sets can be planted during mid-March through to mid-April.

Mid-April to early May
Heat treated onions are delivered later and planted up to the first or second week of May, will still produce a sizeable crop.

Onions for health

Onions are low in saturated fat and sodium, but high in dietary fibre, vitamin A, C, K and Folate. For years onions have been used as one of the oldest medicines for their anti-bacterial, antiseptic and anti-asthmatic properties. They have also been shown to lower blood pressure and cholesterol levels.

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