Shot August 2014 at Reford Gardens, Quebec.

Heat is important when you want to grow things in your garden. That’s pretty self evident, particularly when you’re staring out a window at a world covered in snow and ice. But I didn’t realize just how much heat affected growing things until digging deep (har, har) into my latest course on organic horticulture through Gaia College. Stop me if you’ve heard these before:

WHY SOME BEDS NEED TUCKING IN MORE OFTEN: Early on in studying organic horticulture you learn a lot about composting and how things decompose. Essentially, the whole ashes–to–ashes–dust–to–dust concept is taken quite literally and to very satisfying results in organic gardening. That said, you do get into the nitty gritty, including the rate of decomposition. As it turns out, it doubles for every 10°C rise in temperature. So if you’ve taken the time to spread chopped up leaves all over your flower beds in the spring and the temps start to rise, you may find that the beds that get full sun will need to be mulched again sooner than, say, a spot under a large tree where it’s constantly shaded and consequently cooler.

WHY SUNSHINE ONLY GETS YOU HALFWAY TO A TOMATO: The sun delivers good things to growing things. Light was my first guess. But heat is important, too. Heat is energy and some plants need a particular amount of heat units in order to grow, to flower, produce seed and bear fruit that ripens. For instance, if a tomato doesn’t get 1533 heat units, it can’t bring its first fruit to ripeness.

WHY A WARM WINTER CAN BE JUST AS BAD AS A SUPER COLD WINTER: If we have an unusually warm winter, it may affect the bulbs we planted last fall. A lot of popular bulb species need up to 20 weeks of very low temperatures or they won’t flower.

WHY IT’S TRUE THAT THERE’S HOT TIMES IN THE CITY: Choosing plants that work for your hardiness zone is a good start to gardening success but there are climates within climates all around us. For instance, temperatures in the heart of a large city can be higher than the temperature on the same day out in the country. Streets, sidewalks, buildings—all act like heat sponges that keep whatever small patches of bare earth there are downtown warmer in winter. So if you live smack in the heart of a big city and have a patch of earth surrounded by concrete that you want to transform into a teeny garden, you might have better success with plants that are hardy in the zone that’s one up on the warmth scale—unless you live in a building–created wind tunnel. Then all bets are off.

Today, we’re well into October and its T-shirt weather outside here in Southern Ontario. Global warming or not, I’m going to be paying more attention to what’s hot or not in my garden.