When you walk into any garden center to shop this spring, more than likely the first question you will be asked is “What zone are you in?” If you are going to be a successful gardener, you have to first understand hardiness zones, what they mean, and how they pertain to your particular yard.
The concept of hardiness zones was originally conceived by Dr. Alfred Rehder in 1927. His original work was picked up by the Department of Agriculture and published in 1960. Based on 60-year average of minimum winter temperatures, the country was divided into bands, or “zones” based on these temperature readings. Plants that could survive extreme winter temperatures down to a certain degree reading were rated in that “zone.” For instance, if a plant is known to survive an average minimum winter temperature of -10F to -20F then it would be placed in a Zone 5.
Originally the zone map contained 11 zones with number one being in Alaska and number eleven in Hawaii. As climate changes have occurred, the map was updated in 2012 to include an additional zone and our area encompasses four to five of them. Sometimes the zones are even more clearly defined and broken into an “a” and “b” portion as temperature readings get more specific.
Zone 5 takes in most of the Four Corners region including Aztec, Bayfield, Blanding, Cortez, Dolores, Durango, Mancos, Monticello, Shiprock and Towaoc. However, be aware that these areas do vary greatly and even a plant that is rated for a Zone 5 and may survive well in Cortez, may not survive a cold winter in Dolores. That is why there are further definitions down to a 5a and 5b rating. Generally plants in a Zone 5 will survive temperatures from -20 to -10 degrees.
Bluff, UT and Farmington, NM are considered a Zone 6. Winter temperatures in these areas generally only fall to -10 to 0 degrees. People that live farther south in New Mexico are in Zone 7 where the minimum winter temperatures normally only reach 0 to 10 degrees.
While the idea of rating areas into zones is meant to guide and educate the average consumer, it can still be daunting to try to figure it all out. If you are unsure of your particular zone, then it’s best to ask your local garden center for their recommendations.
To further complicate matters, even within a single yard microclimates may exist making the job of figuring out your zone all that much more difficult. Warmer, sunnier, protected areas will support plants with less winter tolerance than areas that are unprotected or out in the open. In my yard, for example, I have certain plants that do very nicely in one area, but refuse to survive when planted in others. Sometimes it’s simply a matter of trial and error to find the plants that work best for you.
Don’t be put off by the concept of zones. Ultimately, knowing which zone your yard falls in will assist you in making great choices that will make your yard and garden a showplace full of happy, healthy, thriving plants!