Simon

I find a soil warming cable to be invaluable except I don't put it in the
soil, but in a box of sand then stand the plants on top. On really cold
nights I pop a blanket over the top and have never yet (touch wood) had a
frosting problem. The warmer you want the soil, the closer you put the
loops of the wire (plus ours is on a thermostat for extra control). The
wattage of them varies depending on length of cable but IMO they are very
economical to run. Bought my original from Two Wests and Elliott but the
latest was from NA Kays (much cheaper but same quality)

--A

Are NA Kays on the web?

Art