Yesterday afternoon, in 95-degree temperatures, I harvested kale, broccoli, Swiss chard, and sugar snap peas. All of these are considered cool-season crops, and I have been impressed by their persistence as late spring has slammed us with some relentless midsummer temperatures this year. The greens and broccoli keep producing when by all rights they should bolt, flower, and go to seed. The sugar snap vines keep sending forth new blossoms when really it’s time for them to wither and brown.
What is going on here?
I’ve been reading a little about microclimates. A microclimate receives a kind of exemption from the rules of the USDA plant hardiness zones, which tend to govern gardeners’ decisions about what and when to plant. (Do you know your zone? If you live near me, you’re in Zone 7b. You can find your zone by zip code at the National Gardening Association website.)
Back to the microclimates: sometimes there are factors, or structures, or topographical/landscape features in tiny, specific areas where the rules simply change. Take my gardens, for example. I have lots of beautiful old oak trees on my lot, and I have had to work hard to plant around the prevailing shade. So while my veggies get enough sun every day to thrive, they do not get a ton of sun. There are little areas in my garden beds that stay pretty cool, and that’s where the kale, chard, peas, and broccoli are.
On the other hand, a mere six feet away, closer to the northern wall of my house, which gets lots of summer sun and therefore radiates heat, the tomatoes are starting to turn red—another microclimate.
As we gardeners encounter the exigencies of global warming, we are going to have to learn to microclimate manage. Therefore it’s probably a good idea to become more aware of the particulars of our own microclimates. Take some time to just study your garden beds over time. Experiment and compare. And do some reading. The best explanation I have found on the internet of microclimates is here, on the Cornell University Department of Horticulture website. The article begins with a great little piece of wisdom from one of their extension agents:
In the real world, we garden in microclimates, not hardiness zones.
Get to know your microclimates!