Get in touch with your inner garden geek

I know they’re supposed to be used outside, but up until now I’ve only employed a maximum and minimum thermometer to measure how cold our house is in winter.

Digital max/min thermometers are not expensive and I get a certain masochistic pleasure about seeing how cold I can stand it before turning the radiators on. You would not mistake our house for the interior of an old people’s home.

However this Spring I wanted to check if the cold frame was actually maintaining a temperature above freezing in the cold nights, so I took it out and lodged it there. This particular cold frame is a raised one, on legs, with acrylic sidewalls allowing sunlight in and supposedly an acrylic top.

Except the cat from next door – or it might have been a fox – chose to jump over the fence from the other side, landed on the flimsy acrylic panels and stove them both in. Thus I had to replace it with an old double-glazed glass panel that sits awkwardly across both.

After a week with the thermometer inside I realised that the term ‘cold frame’ is a misnomer.

It’s more like a chimenea.

The minimum temperature was 0.1 degrees centigrade, the maximum was a massive 58 degrees centigrade. Fifty-eight degrees! And the thermometer was working properly. Forget raising seedlings inside, I decided I could start firing pottery clay in the heat of my cold frame.

Or maybe I could start up as the first Surbiton blacksmith and use my cold frame as a forge.

A more practical use could be in entertaining. Why not invite some friends round for a few drinks on the patio on a fine late Spring evening. When the air turns just a little bit too chilly to sit outside, no problem, get out the cold frame and sit round that. It’s a lot better for the environment than a fire pit. Having made my discovery, I felt like one of those scientists who thought they had pioneered cold fission. The laws of physics were bending out of all proportion in a Surrey garden, with the use of some battered acrylic panels, a piece of cracked double-glazing and some slightly wobbly wooden legs that needed varnishing.

Now I realised why many of the things I had put inside the “cold” frame over the years had died so rapidly on days I forgot to open the lid. They had been hard-baked. Even on days when I did open the casing up, the diurnal change in temperature would have put even the hardiest, most tolerant of plants under stress.

However, having taken my thermometer outside, I’ve started to become a meteorology geek in the garden. Now I cart it round from place to place and explore the temperature ranges of lots of different parts of the garden. Within the enclosed space of a garden there are many microclimates which plants will be sensitive to, and it’s actually quite fascinating seeing the variances.

To do it properly, of course, you need more than one max/min thermometer. Ideally you would have a set-up that feeds live data back to a computer and you could plot the changes, day by day, month by month, year by year. Why stop at temperature? Once you’ve sorted out those parameters you could start measuring rainfall, soil moisture, sunlight hours. So much fun could be had.

As for my cold frame… I’ve written to the National Physics Laboratory in Teddington to see if they’re interested and I fully expect to see it exhibited one day in the Science Museum in Kensington. I don’t mean to sound immodest but there’s probably going to be a Nobel in it, too.