A very mild end of the year has meant the last of the tomatoes and chillies have only just been picked and are overlapping with some early sowing for next year. Various bulbs like shallots and tulips have been planted in pots ready to push forth; in fact some green shoots are already showing. But the main event at this time of year is sowing of onion seed. It may seem early to start onion but I have managed to get some seed from prize-winning strains of heavy onions and to stand a chance of growing into really heavy bulbs they need an early start. I don’t expect to break any records but I know the heaviest onion and leek at the last Harrogate Flower Show were grown in Air-Pot containers, so I am keen to see how big I can grow.
Only moderate heat is needed to get onion and leek seed germinated and once growing they can tolerate quite cool conditions, what the young plants do need is high light levels. A lot more than we have naturally during the gloomy short winter days we are experiencing, so I have dusted off a couple of fluorescent tube fittings for the plants. It is well worth rigging up a well lit sowing station and this set-up is not expensive, I had a couple of salvaged three foot long tube fittings and bought Gro-Lux T5 tubes which emit the wavelength of light needed for plant growth. A simple reflector can be made by glueing aluminium foil to hardboard then the whole contraption needs to be suspended over the seed trays. Using two chains attached to overhead hooks allows the height to be adjusted, the light should be as close to the plants as possible. A big piece of silver Mylar can be draped over the fitting (I used a survival poncho) hanging down both sides of the growing area to create a mini grow tent. A length of cord between the chains can be strung across to form a sort of “clothes-line” for the Mylar. This maintains a space between the Mylar and the light fitting. It is probably better not to have the reflective sheet directly wrapping over the back of the light just in case this causes overheating. My single 30 Watt tube generates a gentle heat which the plants enjoy, but never enclose any light fitting which generates a lot of heat.
The onion plants are getting 24 hour a day light for now, once they are well established and potted-up individually a timer will give a more natural day / night cycle. Germination in the small Air-Pot trays has been very good and I feel the roots will develop well in these for quite a while, but I know the top growers separate plants into individual pots soon after germination. So the best plants will be potted-on individually, but many others will stay hugger-mugger in their trays until they can be planted in the ground. After onions are moved-on of course a warm brightly lit space can be useful for getting a succession of seedlings off to a good start, such as Spring sowings of chillies, peppers, squashes and tomatoes.
I am pleased to see that my Christmas tree in an Extra-Large Air-Pot has survived another year and is pressing up at the glass at the back of the house keen to come inside for the Festive Season, this will be its forth year with us.