Plant Hardiness Zone Map
Gardeners need a way to compare their garden climates with the climate where a plant is known to grow well. That’s why climate zone maps were created.
Zone maps are tools that show where various permanent landscape plants can adapt. If you want a shrub, perennial, or tree to survive and grow year after year, the plant must tolerate year-round conditions in your area, such as the lowest and highest temperatures and the amount and distribution of rainfall.
The USDA Hardiness Zone Map divides North America into 11 separate zones; each zone is 10°F warmer (or colder) in an average winter than the adjacent zone. Zone 1 is the coldest, as it encompasses extreme northern parts of Canada and the interior of Alaska. Zone 11 is the warmest, a tropical area found only in Hawaii, coastal Southern California and southernmost Florida.
We live in the Chicago area which is considered Zone 5 (light green on the map above). If you see a hardiness zone in a catalog or plant description tag, chances are it refers to the USDA map.
The average minimum temperature is not the only factor in figuring out whether a plant will survive in your garden. Soil types, rainfall, daytime temperatures, day length, wind, humidity and heat also play their roles. Even within a city, a street, or a spot protected by a warm wall in your own garden, there may be microclimates that affect how plants grow.
So remember, zones are a good starting point to determine the best plants for your garden, but they are only a guide.
Click here for a handy tool to determine what zone you live in: Plant Hardiness Zone By Zip Code