What are hardiness zones?
The U.S. Department of Agriculture’s Plant Hardiness Zone Map divides the United States and Canada into 11 “hardiness zones” based on average annual minimum temperature (plus or minus a 10 degree Fahrenheit difference). The United States falls within Zones 2 through 10. These zones represent an area of winter hardiness for agriculture and landscape plants. (Generally speaking, it indicates what plants will survive winter weather in your community.) Plant Hardiness Zones… Zones 2-10 in the map have been subdivided into light- and dark-colored sections (a and b) that represent 5 F (2.8 C) differences within the 10 F (5.6 C) zone. (See map and map key below.) The light color of each zone represents the colder section; the dark color, the warmer section. Zone 11 represents any area where the average annual minimum temperature is above 40 F (4.4 C). The map shows 20 latitude and longitude lines. Areas above an arbitrary elevation are traditionally considered unsuitable for plant cropping
It seems every gardening book and nursery catalog refers to plant hardiness zones, also known as climate zones or growing zones. If you’re new to gardening, you may be wondering what all the fuss is with these zones, and how to find out which zone you are gardening in. Basically, plant hardiness zones are a guide to help you know which plants will grow where you live, so you don’t plant things that will soon die just because they can’t manage your region’s temperatures. Plants vary in the temperature extremes they can endure. Basic laboratory testing can determine the lowest sustained temperature a particular plant type can withstand, but, as gardeners, we still need to know how these measurements relate to our own gardens. USDA and Canadian Hardiness Zones In an attempt to answer this question, years ago botanists and horticulturists started gathering weather records throughout North America to compile a database to show the average coldest temperatures for each region. These records
