Warming A Polytunnel

[Oola]

A lady commented on my Smallest Smallholding blog today. She's based in Scotland and asked me if I have any ideas of how she can warm up her polytunnel in winter, so that they grow more veg all year round.

Any ideas? All I can think of is the specialist polytunnel covering and siting the polytunnel's entrance away from prevailing winds.

[lily]

I don't have the answer but am very interested in polytunnels- quite fancy having one. I would have thought the light levels in Scotland would have been against growing much in the winter with or without the tunnel? I know some people use bubble wrap inside greenhouses, maybe it would work in a tunnel? My local National Trust have a lovely tunnel with a sort of mesh outer layer, but don't seem to use it in winter. Very interested to know if any musers have experience of tunnels.

[Pippa]

I work in polytunnels and they are very draughty and difficult to heat. I would have thought the easiest plan would be to section a piece off with plastic or similar, so have small part to heat. An electric greenhouse heater, if there is a supply might be an idea, they click in and out on a thermostat. We used to have parafin heaters, but I expect that is expensive now. Depends how much heat you want really, some light bulbs give out a lot of heat and some crops grow well in a tunnel if free from draughts and frosts.

[lily]

Hello Pippa, I'd like to know a bit more about polytunnels- what sort of crops do you grow in them and would you think they are a good idea for all year round vege supplies? Very grateful for any information, my gardening magazines and books don't seem to make much mention of them.

[Pippa]

The tunnels at work are mostly for protecting plants, acer, bamboo, palms and the like from the elements during the winter. They are VERY draughty but I think you could grow some veg. but the light levels would be the problem in the very short months. If the polytunnel is thick plastic I find they do keep fairly warm as they keep the wind off so maybe would not need too much heating, if plants kept away from the sides they should be safe from frost (in West Devon) and salads, potatoes would be my first thought. Aphids may be a problem in an enclosed area, it really is getting the balance between gentle ventilation/howling gale!

[lily]

Thanks Pippa, you're the first person I've "known" who has experience of a tunnel.

[Pippa]

Believe me Lily, working in a tunnel is not what is cracked up to be! We have to stand for hours picking the tips out of hedging shrubs to make them bush up, it must be like picking tea in India. The clematis are always falling over and then you discover something dead at the back, oh joy. I hope to have a new greenhouse at home for the winter and hope to grow some salad leaves and early pots. I have heard you can grow potatoes in a tub ready for Christmas dinner.