Information about plant hardiness zones and the USDA map is online at www.usna.usda.gov/Hardzone/
Steamboat Springs Driving down the road into town last week when it was 40 below zero, I felt sorry for the poor horses and livestock and wild animals that had to stay outside in this frigid weather. I know they have winter coats of fur and such, but still.
Then I began wondering about some new trees and perennials I put in the garden last year. I’m sure many of us are wondering how our gardens will survive when temperatures drop below the norms for our Zone 4 area.
Native plants and Zone 4 hybrids grown for our region are designed to withstand temperatures that drop as low as 30 below zero.
Native plants for our area have genes that tell them when to start hardening off and become tolerant to our freezing temperatures. In
fall, these plants and others that have adapted to our environment moved the sugar and nutrients from their foliage into their stems, branches and roots to provide them sustenance through the winter. They stopped growing
shortly before our first snowfall in October.
As the weather got colder, the plants began to thicken their cell walls and create an anti-freeze-like substance within the cell to protect it from damage. Generally, this anti-freeze substance is good at about 14 degrees. Hopefully, either the mulch we placed around the roots of our plants, or the snow cover, is helping keep the worst of this below-zero weather away from the stems and roots of the plants.
In another stage of preparing for winter, the plant creates another chemical or enzyme that keeps the plant from dehydration or drying out because of limited water intake and the fierce, cold winds we experience during the winter. At this stage, the plant can handle temperatures as low as 22 below zero.
And when temperatures get really cold here, like what we experienced last week, stage three changes take place. Those changes are described as a type of plant cryogenics. This involves the plant forming some type of vitrification, or glass formation, with smooth edges rather than sharp edges so as not to destroy plant cells. Not a lot is known about this stage, which disappears quickly, with just a few hours of warmer temperatures.
So, if you have native plants in your garden, they know what to do in this arctic weather. If your plants are non-native, they may have a few problems coming into spring if they weren’t protected enough by mulch or other coverings.
For more information about this process, our local botanist, Karen Vail, recommends “Winter: An Ecological Handbook,” by James Halfpenny and Roy Douglass Ozanne.
Deb Babcock is a master gardener through the Routt County Cooperative Extension Office. Call 970-879-0825 with questions.