Hartley Magazine

All the latest news, hints, tips and advice from our experts

Onion Sowing

Image 1 - Dec 2016
Onion seeds can be sown in the greenhouse in December

There is almost no month in the year when you can’t be sowing something in the greenhouse, if you really put your mind to it. As if to prove this I have found myself heading down the garden these last dreary days with a packet of onion seed, just like the monster veg growers. The monster veg growers reside in one of my favourite nerdy corners of the internet. Among the kitten videos, the flower pictures and the jokes at Donald Trump’s expense that my twitter feed routinely throws at me, there occasionally appear the workings of a competition grower. They sow seed outrageously early, sometimes into drainpipes full of soil. They feed and primp and keep their vegetables growing steadily for the longest possible period, the drama culminating around August or September in a single, understated photograph of five lengthy and perfect carrots laid upon a paper plate and crowned with a rosette.

These vegetable growers sow their own onion seed. Most of us grow onions from sets, which speeds up the whole process and means you can pop your onions direct into the ground. But the small bulbs that make up sets are prone to bolting if they are not heat treated, and only a limited number of varieties can be heat treated, and so competition growers tend to just start early and choose their favourite types. I have no interest in growing for competition and doubt I have the patience or the attention to detail to get anywhere near a top three placing, but i am interested in different varieties, and particularly in the sweet onions that are impossible to heat treat and so are not available as sets. Seeds are far, far cheaper too, and you can produce a great number of sweet and lovely onions for a fraction of the price of perfectly ordinary sets. ‘Liria’ is a sweet Spanish onion named after the Valencian town where it is widely grown, and sown now will make lovely big onions for autumn. ‘Lusy’ is from the Czech Republic and is a perfectly round and yellow onion that stores very well. You would struggle to find either as sets, but you can buy both as seeds from www.realseeds.co.uk

Care for ordinary onion seedlings is pretty straightforward. Start with fresh seed, as onion seed declines quickly, and you will have patchy germination with older seed. Sow them across a tray of seed compost and then give a little bottom heat. Ideally this would mean placing them in the greenhouse on a heated propagation mat, hence ensuring that they are both warm and well lit, but if you don’t have heat in the greenhouse you can still start them off in a warm spot indoors – on the top of the fridge is ideal – and transfer them to the greenhouse once they have germinated. They are perfectly hardy and wont need any protection other than the house itself, they just need that little bit of heated help getting off the starting blocks. Once they are growing well keep them watered, and consider potting them up into larger containers as they get bigger. When the soil has warmed a little, around April time, you can set them out into your vegetable plot. Fill a trench with compost and settle the onion seedlings in, then keep well watered and weeded. Little spindly onion seedlings find it hard to compete with weeds, so plant rows of rocket, lettuce and other salads alongside to help keep the weeds down, and then get in close and hand weed regularly. By next autumn you will have produced a huge crop of sweet and storable onions from a near-midwinter greenhouse sowing.