What Is the Map? What Is Your Zone?
The US Department of Agriculture produces a map for gardeners based on the average of low temperature readings taken from weather stations throughout the United States. The idea is to give the garden industry a way to communicate the cold hardiness of landscape plants. That is why the tag of a holly or any other landscape plant often says “hardy to zone __.”
Of course, the map also provides vegetable and herb gardeners like you with a rough guide to the extent of cold where you live. Many of our perennial flowers and herbs are hardy as far north as zones 3 or 4. Cool-season vegetables, most of which tolerate or even like a little frost, will grow well in zones 7 and southward in the fall. This is roughly where we distribute transplants to your local garden center at the proper time for planting.
|USDA Hardiness Zones and Average Annual Minimum Temperature Range 1976-2005|