It’s been a mellow and mild autumn, and I have been tricked into not quite believing it would ever turn cold. This is a handy state of denial if you own a greenhouse, as lining the walls and doors for winter is truly one of the dullest jobs of the year: hours of painstaking fiddling with bubblewrap and little plastic attachers, and in the past it has taken me several weekends in a row (with frequent child-based interruptions) to get the whole thing sealed up and cosy.
Well it has finally turned cold and so the job looms, except this year (to the detriment of my tomatoes: I wont do it again) I left my bubblewrap up all year so the bulk of the work is done. What I must do though is fill up the water butt to keep the place warm. It’s unfortunately not connected up to a downpipe, and so this means a good degree of ferrying water up and down the garden in watering cans. Perhaps a water butt full of cold water doesn’t sound like an especially effective heating system to you, but while it doesn’t have the warm glow of a greenhouse heater what it does boast is thermal mass. Essentially, things with thermal mass warm slowly and cool slowly, so while my water butt full of water got extremely cold last winter, it never actually froze solid, while anything outside of the greenhouse did. By staying unfrozen it must have regulated the temperature of the air around it. Admittedly it wasn’t enough to keep my pelargoniums alive through the searing cold, but still, it was perhaps a degree warmer in there than it would have been otherwise, and in the depths of such a winter, a degree counts for a lot.