Received wisdom has many kitchen gardeners starting their onions off from sets – small, immature bulbs that swell to a respectable size within a few short months. But while sets are speedy, convenient and generally reliable, it’s worth noting that onions will also grow handsomely from seeds sown in the dark depths of winter. With all quiet on the vegetable front, it is reassuring to be doing something now that will carry us through to the new growing season that’s just weeks away.
The New Year is a great time to try a new technique, and they don’t get any more efficient than onions raised from seed in module trays. If you’re anything like me then, after taste, the next reason for growing your own vegetables is cost. Home-grown produce can save literally hundreds of dollars, while implementing evermore ingenious ways of driving down the grocery bill is all part of the fun! Onions from seed offer a budget alternative to sets and take minimal extra effort, so why not give them a try?
An Early Start for Onion Seeds
I have often grown onions from seed. It is only forgetfulness on my part that has me turning to sets later on in spring as a means of catching up. You can sow maincrop onions under cover anytime from the turn of the year to the end of February. If spring is later to arrive where you are then sow towards the end of this timeframe (even later in very cold climates) to be sure that the ground will be ready to receive your pungent transplants once they are big enough to go out – you don’t want the soil to be too wet or cold.
The way to streamline the whole seed-sowing process is to start the onions off in the same module trays from which they will be planted out in spring, thereby doing away with the need for any fiddly pricking out. Use trays with cells that are about 2-3cm (1in) across the top and pack them with quality multipurpose potting soil that’s been sieved to remove any lumps. Make a slight depression in the surface of each cell and drop a modest pinch of seeds - about five to eight - into each. A good tip is to pour the seeds into your hand before sowing – it’s easier and more accurate to count the black seeds against your palm than drop them straight in from the seed packet and hope for the best! A steady hand and a pointed knife to portion out the seeds will ensure an even cell fill.
Once the seeds are in their cells they can be covered back over with a further sift of compost, watered carefully then popped into an unheated propagator to germinate. Don’t worry if you haven’t got a propagator – a sheet of glass laid over the top of the tray will make all the difference. To ensure the darkness necessary for germination cover the glass or propagator with a double-layer of newspaper.
Growing Onions On
Remove the newspaper as soon as the seedlings poke through, followed by the glass/propagator lid when they touch it or the hooked seedlings have unhinged themselves. The seedlings can now be grown on in the greenhouse or cold frame until they are ready for planting out in early to mid spring.
One of the joys of starting onions in this way is that there is no need to thin out the resulting seedlings – they can be set out in clusters, exactly as they are. Too crowded surely? Well no, as over time the individual plants will simply push each other apart, elbowing their siblings out of the way to make sure they get the space they need. You won’t get any king-sized bulbs this way but you will get an ample supply of storable, mid-sized bulbs that are perfect for the kitchen.
To give your onions enough room to spread out they will need a little more space than would be typical for planted sets. Rather than the usual 15x30cm (6-12in) spacing, opt instead for a generous 36-40cm (15-16in) apart in each direction. Far from being an extravagant use of space, the cluster arrangement of onions will ensure you get a surprisingly hearty haul from your onion patch. If pests of any description are a problem protect your young plants with a covering of garden fleece until established.
The Easy Part of Growing Onions
If you have planted into fertile, firm ground in a sunny spot of the garden then it is pretty much job done from here. You’ll need to whip out any weeds that attempt to compete with your onions but aside from that they should put on girth as fast as the passing year puts on day length. By the end of summer the onions will be ready for lifting and storing following a period of drying.
So what to grow? Many maincrop varieties of onion are available as seed. The most popular that turns up time and again is ‘Kelsae’, a golden onion whose tendency to produce good-sized bulbs serve it well in this relatively crowded, clustered setup. It’s also worth seeking out seeds of ‘Globo’, a newcomer to the scene that’s formed even bigger bulbs in trials. Both are widely available.
By Benedict Vanheems.