Medwyn Williams explains the importance of temperature
Giving plants a helpful push along indoors is a fine balancing act
My onions are doing quite well and are now potted up into 9cm (3½in) pots, growing away nicely under my lamps with a minimum temperature of 13C (55.4F). I don’t believe in pushing these plants too fast as they’ll only get too large too quickly at a time when it’s too cold for them to be planted out in the polytunnel.
At my masterclass weekend in November, I was given some onion seedlings by Bill Jones from Wrexham. These were from the Peter Glazebrook world record strain and Bill had sown them very early in October. I left them on the bench in my greenhouse, but it soon became apparent that Bill must have had them growing at higher temperatures than me. Within a week of being in my greenhouse they never grew on and many of them died off.
However last month Bill very kindly brought me some more of these plants and I shall certainly have a good go at them. It just goes to show how different temperature regimes can affect the plants, particularly out of season.
My idea at the moment is to dismantle my 9m (30ft) tunnel at home, bring it over to the land and erect it on concrete blocks. I’ve already removed the polythene from the roof and it shouldn’t take more than a day or two to dismantle. I’m going to grow nothing but leeks and onions in
this tunnel in raised concrete
block beds. If I don’t have time to do this, I’ll grow the leeks in 30 litre pots in my large polytunnel, where I’ve had some excellent results with both the blanch and pot leeks. Last year I grew the leeks on a bench in my glasshouse though I have to say that they seemed to grow bigger and better in the polytunnel. I’m not sure why, but it could be something to do with the more diffused light that comes through the polythene.