How to Use Plant Hardiness Zones

Photo of Hardiness zone flowers

For most new gardening fans, one of the most fun parts about setting up your first garden is trying to determine which plants to grow. Knowing how to use plant hardiness zones will help you do this!

When you check any of the major gardening guides, you will likely come across a few “quick facts” lists that tells you the best conditions for each plant to thrive in. And 99% of the time, the USDA Plant hardiness zone is right below soil type and water. That’s how important it is!

This very popular label is one of the most efficient ways to classify plants according to the cold temperatures they can resist. But do you know what it means exactly?

Well, let’s find out below!

How to Use Plant Hardiness Zones

The plant hardiness zones is a classification method invented by the United States Department of Agriculture (USDA). Follow these steps to learn how to use it properly.

Understand What Plant Hardiness Zones Means

Plant hardiness zones are meant to help you find plants that can survive through the winter where you live.

This “hardiness rating” is decided by the average annual minimum winter temperature of each area. There are 11 Hardiness zones around North America. Each one covers a range of 10° Fahrenheit. Lower hardiness ratings represent lower temperatures:

  • Zone 1: Minimum temperatures below -50° F
  • Zone 2: -50° to -40° F
  • Zone 3: – 40° to -30° F
  • Zone 4: -30° to -20° F
  • Zone 5: -20° to -10 ° F
  • Zone 6: -10° to 0° F
  • Zone 7: 0° to 10° F
  • Zone 8: 10° to 20° F
  • Zone 9: 20° to 30° F
  • Zone 10: 30° to 40° F
  • Zone 11: 40° to 50° F

Keep in mind that these temperature ranges are supposed to be the minimum average temperatures. There’s always the occasional cold year where temperatures in a city that’s supposed to be in Zone 4 may go below -20° F.

For the most part, the guys at the USDA managed to establish good predictions. Can you tell, off the top of your head, what plant hardiness zone are you living in?

Check the USDA Plant Hardiness Zone Map

Hardiness zones

The easiest way to check which zone you are in is to visit the USDA’s website and check their official USDA Plant Hardiness zone map. Visit it here and zoom in to find exactly where each town falls!

If you are in the United States, you can also enter your zip code and see the results immediately. You will just need to fool the quick CAPTCHA and prove you are not a robot.

Check your local climate conditions

Now that you know which zone you are living in, you will have gained a lot of information on your regular winter temperatures.

For example, if you are in Zone 1, 2, or 3, you probably live in Alaska, or in a Northern mountainous region. Most of the country falls under zones 4 to 8. Zone 11, on the other hand, only covers some tips of Florida and the whole of Hawaii.

The next challenge is to find a hardy plant that can survive your winter.

Research the plants you want to grow

At this point, you have two choices:

If you don’t know where to get started with your new garden, you can simply google which type of plants grow well in your climate zone. Just look up “trees”, “shrubs”, “vines”, or “flowers” next to your hardiness zone and see what comes up!

As a general rule, you will see that lower numbers yield fewer plants. In zones 1 or 2, you may just find small trees and very hardy grass. Vines will most likely be confines to zones 7 or above – but there are always exceptions!

So what if you already have a selected plant in mind? Then, just make sure it is suited for your area. In this case, just go to your favorite gardening or growing guide, find your species, and look at its plant tags.

You can also try to google the plant’s scientific name and add “live in zone”. For example, for Coralbell flowers, look up “Heuchera live in zone”

Match the local hardiness area with the plant’s hardiness

The idea here is to ensure the plants for your garden can survive the winter in your climate zone. This means that the hardiness zone doesn’t need to match your zone exactly!

If you want to grow a perennial (that is, a plant that can last for many years, such as most bushes and trees), make sure the plant’s zone is either the same as your area or lower.

For example, the coral bells we mentioned above are only mildly hardy plants and belong in zone 6. If you live in zone 7 or 8, they will have no problem. If you live in zone 5, it may be too cold for them.

If you want to grow an annual plant (like most flowers or garlic), then the task may be easier. Annual plants are those that can go through their entire growth cycle, from seed to fruit, in a year. They don’t need to be very cold hardy: just plant them at the start of the spring to make sure they get enough time to grow before winter arrives.

Adapt to your findings

USDA Climate zones are considered the standard for plant hardiness across North America. However, they only tell you about the minimum average winter temperatures, so you will still need to care for the plants in your garden properly.

In addition to heat, plants will also need enough water, sunshine, and the right type of soil. You can find this information in the plant tags section in most gardening manuals. You’ll also need to prune it or mulch it properly!

If you live in the West Coast, especially near the Rocky Mountains, you should also look up your Sunset Climate Zones. This classification is more accurate for places with a high altitude.

Finally, remember to keep an eye out for any unusual weather! When trees and other perennials are still young, they can be particularly sensitive to any abrupt dips in temperature. Even if you are in the right hardiness zone, you may need to bring some potted plants inside if there is an early frost. You can also try to protect them with a plastic tent if a freak storm hits your area.

Final Thoughts

As a new “plant parent”, you will find that researching the life cycle of your new babies is important. Sometimes, the research stage can be as fun as the actual growing and yard work!

Learning how to use plant hardiness zones will help you decide whether your new plants can survive the winter. The USDA Plant Hardiness zones map will help you find cold-hardy plants that have the best chance in your area.

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