Turn up the Heat

Use thermal mass to increase the amount of heat your figs get.

Use thermal mass to increase the amount of heat your figs get.

Around here, we’re only a couple of months away from that first fall frost that puts an end to any hope of ripening more figs.For someone like me, with no background in energy, the comment sounded profound; yet so simple.

The alternative energy expert (whom I interviewed about home energy generation) told me not to forget “thermal mass,” which, he felt, is as important as generating energy. In his projects, he combined solar and geothermal technologies with the idea of thermal mass.

What he meant by thermal mass was using building materials that capture and then slowly release heat, materials such as tile and concrete. It was very logical, of course, but I’d never thought about it before.

We’re in the middle of a heat wave here in the Toronto area. Yet already, the nights are becoming cooler. As temperature swings between day and night become greater, using thermal mass in the garden is a technical-sounding, yet simple way to given fig plants more heat. Remember: More heat for our fig plants means more ripe figs before the fall frost arrives!

If you already have your fig near a paved driveway or brick wall, then it’s benefitting from thermal mass. At night, the driveway or brick slowly radiates heat that has been stored during the day, keeping the air temperature around your figs a bit warmer.

I was reminded of this a couple of weeks ago when I visited my friend Andrea, who recently planted a fig hedge (which she intends to overwinter with an insulated A-frame). As I stepped—barefoot—onto her patio, the dark stone singed my feet. It was scorching hot. When it rained a short while later, the stone dried within minutes because it was so darn hot!

Andrea’s figs have a really great “micro-climate.” They’re surrounded by that heat-capturing and heat-radiating stone. At night, those figs bathe in radiated heat. All thanks to thermal mass.