Understanding Growing Zones Using A Hardiness Zone Map

Written by: Luke Marion

Published on December 19, 2016

Updated on October 15, 2025

Knowing your growing zone and understanding the hardiness zone map are crucial gardening facts you need to know. But, when it comes to growing zones, I’ve seen a lot of misinformation and misconceptions out there!

A hardiness zone map of the United States.

Believing the myths can stifle gardeners, causing them to be fearful or stop growing certain crops (regardless of if they live in zone 5, 6, 7, 8, or 9). I want to help you apply growing zones correctly because it can really help you as a gardener!

Whether you want to plant a fruit tree or start a vegetable garden, let’s simplify things and dispel all the myths surrounding growing zones!

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What Is A Growing Zone

A growing zone is a geographical location assigned a number based on the average minimum winter temperature there. The zones are numbered 1 to 13; the lower the number, the colder the average lowest temperature.

Each zone represents a 10°F range and can be further divided into sub-zones of 5°F increments. For example, zone 3 has an average low temperature of -30°F through -40°F. The USDA plant hardiness zone map further breaks it down into sub-zones 3a, with an average low of -40° to -35°F, and 3b, with an average low of -35° to -30°F.

What Does a Growing Zone Indicate

The growing zones indicate a crop's survivability in that area and the average lowest temperature that a crop can experience during winter over a 10-year rolling cycle. You may be surprised to learn that this only impacts perennials (because perennials need to survive winter).

Regardless of what perennial plants you grow, they all have a coldest temperature that will kill them. Some winters are just too harsh for some perennial plants. So, the growing zones were created to help people know which perennial plants they can successfully grow where they live.

Your growing zone doesn’t directly affect growing annuals or when you should start seeds! Pro-Tip: Annuals are crops that you grow and harvest yearly within your growing season, but they won’t survive the winter. The information you actually need to grow annuals is the estimated first and last frost dates, which determine the length of your growing season.

Now, it’s true that your average coldest temperature (your growing zone) and first and last frost dates are loosely correlated. But there are places where it may get very cold in the winter, yet they still have a long growing season, like the high desert in Arizona.

How to Use a Plant Hardiness Zone Map

A map showing plant hardiness zones 1 through 13.

To find your exact growing zone, use the USDA plant hardiness zone map. Follow the link and enter your zip code in the search box at the top of the map. You can then zoom in or out and click and drag the map to find your exact location.

Match the color that shades your location to the map key on the right-hand side of the page. This will tell you your growing zone.

Now that you know your zone, you can look at the hardiness zone recommendations when you are shopping for plants or seeds. This information tells you if that plant will likely survive winters in your climate.

You Can’t Grow That!

A common growing zone misconception I hear is gardeners claiming that you can’t grow perennial crops that are not recommended for your growing zone. In reality, you can grow any crop you want in any growing zone, just don’t expect them to survive the winter.

A prime example is that I grow artichokes in zone 6a. Artichokes are known as tender perennials with a survivability range of zones 7 to 11. But that doesn’t mean I can’t grow them! I was able to grow and harvest artichokes in a single season. The winter cold killed the plant, but I still enjoyed fresh home-grown artichokes!

Another crop that I grow is rosemary. It will sometimes survive the winter weather that 6a throws at it, but its survivability range is closer to 6b or 7. While it may or may not overwinter in my zone, I can grow it, enjoy it, and replant if needed.

Growing Perennials Indoors

You can also grow perennial crops with survivability outside of your growing zone by bringing them indoors during the winter! I grow citrus in containers in growing zone 6a and they are sitting near a sunny window, just loving life.

These plants are grown outside in the heat of the summer and brought indoors before the weather gets too cold for them. Here are some other crops that you might want to grow this way:

Cacti - Cactus is fun to grow, adding texture and color to any space.
Dragonfruit - MIgardener has 3 stunning varieties of dragonfruit for you to try: Purple Dragonfruit, Yellow Dragonfruit, and White Dragonfruit.
Coffee - Coffee is the most consumed beverage in the world, and now you can grow your own!
Banana Trees - How fun would it be to grow your own bananas in containers?!

Cold Hardy Varieties

When you don't think a crop will survive in your zone, some varieties may! There are quite a few crops with cold-hardy variants! Not every variety in a subset will follow the same hardiness rule. There are outliers, and some may be more cold-hardy.

Some examples are:

Figs - While any other fig variety would die in my zone, the Chicago Cold Hardy fig can tolerate zone 5, and we’ve been growing it for years.
Almonds - Almond trees are typically grown in zones 7 to 9, but Hall’s Hardy Almond tree is known to withstand cold winters down to zone 5.
Pomegranates - The Russian pomegranate can tolerate zone 5 or 6, no problem, while other pomegranate varieties would die below zone 8.
Avocados - Avocados grow in very warm climates, but there are several varieties that tolerate colder weather.

Ask your local agricultural extension or local farmers (or even other gardeners) who have been growing in your area to get a better understanding of how certain varieties might fare. Do your research to find those unique varieties so that you can grow bigger!

Is zone 7a warmer than zone 7?

Each zone represents a 10°F range and can be further divided into sub-zones of 5°F increments, so zone 7a is a subzone within zone 7. Zone 7 has an average lowest temperature of 0° to 10°F, while zone 7a has a more narrow range of 0° to 5°F.

What is the difference between zone 4a and 4b?

Zone 4a has an average lowest winter temperature of -30° to -25°F while zone 4b has an average lowest temperature of -25° to -20°F.

Can anything be planted in September?

What you can plant in September depends on the number of days left in your growing season. For more information, read What to Plant in September and Fall Garden Plants.