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Cold and heat zones

By: Garden Gate staff
Not sure what your garden’s cold or heat zone is? Find out here. (And learn why it matters.)

How do you know if a plant you love will grow in your garden? Check its cold and heat zones. Keep reading to learn what those are and how they affect you.


Know your cold-hardiness zone

Cold hardiness is the ability of a plant to withstand a minimum temperature. This map creates zones based on average annual minimum temperatures throughout the United States. A plant’s cold-hardiness zone rating indicates where it’s likely to survive the winter. The map was first published in 1960 and has been updated several times since then. The original ratings of some plants have changed as more data has accumulated. New plants are tested and rated for cold hardiness before they are released to the public. Temperatures across the country are monitored to keep the map up to date.

Want to see exactly where you are? Check out the USDA's zip code tool here.

Looking for Canada's zones? Here they are.


Know your heat-tolerance zone

Is heat a bigger concern for you? This map divides the United States into 12 zones to indicate the average number of heat days, or days in a year when the temperature goes above 86 degrees F. That’s the temperature at which plants begin suffering and are unable to process water fast enough to maintain normal functions. Zone 1, the coldest zone, has less than one heat day. Zone 12, the hottest zone, has more than 210 heat days per year.

One caution about zones:

They're only guidelines. Don’t let them limit you. Experiment with cold- and heat-protection to grow plants that supposedly aren’t hardy in your zone. With mulch and by creating microclimates, you can sometimes “push” the zones of some plants.

Published: March 9, 2018

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