Identifying plants that are adapted to Utah's climate
Soon advertisements from nurseries will come into your mailbox or email inbox. Most years nurseries have new offerings of various plants that are sure to make your life better and your home more beautiful. Often, the catalog descriptions will include a reference to USDA hardiness zones.
Using thirty-year data sets, the US department of agriculture produces maps that reference the coldest winter temperatures that may be experienced in general areas. In the eastern united states, the maps mostly reflect latitude and the hardiness zones cut wide swaths across the south and Midwest. Mountainous areas of the west are more challenging.
Here, cold winter temperatures are a function of altitude and air drainage, not just latitude. Cache Valley is mostly in Zone 5, suggesting that our coldest midwinter temperatures would not exceed -15 to -20°F. Most of the Wasatch Front is in zone 6, suggesting midwinter cold temperatures would not drop below -10°F.
The hardiness zone maps help gardeners identify plants that are likely to survive the winter temperatures typically experienced in a given area. For ornamental plants this information is very useful. It helps us choose plant materials that are adapted to our climate and that won’t be killed by winter cold.
However, the hardiness maps don’t give a complete picture for other species. For example, Heber City is in hardiness zone 5b, suggesting midwinter temperatures would not drop below -15F. That is likely true. But, Heber City only has about 90 frost free days during the summer.
The median last spring frost is June 15 and the medial first fall frost is September 10. Ninety days is not long enough to mature most tree fruit crops. Even the earliest apples will require 110 frost free days.
Historical frost dates for your area can be found on the website of the Utah Climate Center. This information combined with hardiness zone maps will give you a better idea of fruit crops that can be successfully grown in your location.