Bozeman Montana. 2:00 p.m. 58°F in the sun (46° in the shade) and I’m out in my driveway in a sleeveless shirt shoveling off the last of the ice that hid in the shadows. I had a sweater on to start, honest, but it was just too hot! Any time I’m engaged in gardening in my front yard it is an invitation for neighbors to come over and ostensibly see how I’m doing since Dr. Bob passed, and often their visit includes a gardening question or two.

The obvious one with this type of weather in January is, “What’s going to happen to our trees and shrubs?” We’re all worried that this spring-like weather will force our woody plants to break dormancy, only to get hammered by the inevitable cold weather that is yet to come. Woody plants in our area have something called a chilling requirement. After our deciduous plants have hardened off in the fall and drop their leaves, they enter into dormancy. We all know that. What folks don’t always know is that the first phase of dormancy is called dormant-rest, in which plants’ physiological processes simply cannot begin until they’ve had a certain number of hours at low temperatures. To overcome rest, buds must be subjected for about 4 to 8 weeks to temperatures of 24° to 50°F.

As you can imagine, the temperatures and length of time differs between species. This is not well studied, nor is it documented for many of our plants. We do know, for example, that apples usually require a longer chilling than do peaches, which is one of the reasons peaches don’t do well here. They break rest before winter loses its hold for the year. After the chilling requirement has been fulfilled, the plants are in a state of dormant-quiescence. In this state they are ready to go, and are simply waiting for appropriate spring temperatures to get in gear. Kind of like seeds waiting for the appropriate conditions to germinate. In many locations our fall was not as cold as we typically see, so we can all cross our fingers that our woody plants are all still safely in dormant-rest.