Onions will warm to an early start

Onions for showing.
Onions for showing.

We’re barely a week into a new gardening year and I’m already feeling the buzz of anticipation.

It comes from onion seed sown on Boxing Day as tradition dictates, and from flowers opening on some favourite indoor plants.

Onions growing for size.

Onions growing for size.

Onion seeds need a little artificial warmth to kick-start germination at this time of year, 12 to 15 Celsius will suffice, but our large greenhouse is not heated.

This left two options: the airing cupboard with its hot water tank or the conservatory. Although the former does retain a warm, occasionally hot environment, it is dark and seedlings are removed quickly after germination to prevent them becoming leggy. The conservatory was a better choice.

The presence of several tender potted plants that have grown into decent specimens prompted us to concede that modest warmth was necessary over winter. The proviso being that overcrowding does not spoil the chi.

So two small trays received John Innes compost, mini seed drills were made with the edge of small ruler and a covering of vermiculite then water completed the onion sowing. Cling-film sealed the trays and will conserve moisture until seedlings appear.

Although as with most seeds this is anticipated within 10 to 14 days, it does not stop eager gardeners looking for signs of germination after two.

When they’ve fully emerged in shepherd’s crook fashion and reach two centimetres, transfer them to individual pots with soil-based John Innes compost.

Sowing this early gives the plants time to fully develop and ripen for autumn storage. If they reach a reasonable size and shape, with a good finish, you can even display them at your local show.

You may think that sowing the seed now is rather early but some dedicated exhibitors started theirs back in late September. They grow them entirely under cover in a poly-tunnel, and offer supplementary lighting to maintain steady winter growth.

Acquiring or developing your own show-worthy strain of onion is essential. The seeds you sow should ideally have come from a plant that has proven ability to excel in size and shape when cultivated well. Successful exhibitors often sell any excess of seed or plants. They are also advertised in the gardening press and appear for sale at garden centres.

Although buying a packet of Kelsae, Ailsa Craig or Robinsons Mammoth Improved onion seed is a reasonable start, it can take a few years of selective breeding before the dream onion appears. Meanwhile, ensure the growing bed is in a spot that enjoys warmth and light, and has a balanced organic and nutrient content.