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What Is a Plant Hardiness Zone? (And Its Role in Whether Flowers Come Back)

by | Updated: Sep 9, 2021

When you buy a flower plant…

You may notice a strange phrase on the plant tag that says: “Hardiness zones” or “Zones.”

If you’re wondering, “What is a plant hardiness zone? What does that mean?”, you’re in the right place.

This plant tag says USDA plant hardiness zones 5-9.

At its most basic, a plant hardiness zone tells you whether a plant is likely to survive the winter temperatures in your area.

It’s a helpful concept to understand because it can play a role in whether your plants will come back or not.

I like to think of a hardiness zone like a jean size

Think, for a moment, about your favorite pair of jeans.

It helps to think of a plant hardiness zone like a jean size.

When you put them on, they fit you like a glove. They feel good. They make you look good. They make your butt look good.

YOU. LOVE. THEM.

Sure, you could wear a size or two bigger, but they just wouldn’t feel right.

And yes, it’s possible you may be able to s-q-u-e-e-z-e into jeans one size smaller — with the help of some serious Spanx or extra reps at the gym. But your jeans REALLY wouldn’t feel right. You wouldn’t last very long in them.

Nope, there’s a sweet spot.

Your favorite jeans are the right size for you.

Your garden is like your beloved pair of denims: It has a sweet spot too

It’s “size” is known as its hardiness zone.

And that zone number tells you which plants should be the right fit for surviving winter and returning in your garden next year.

You can try planting flowers that don’t fit your garden’s plant hardiness zone, but they’re less likely to return.

Luckily, you don’t have to become a meteorologist to figure out your zone

Feeling confused like this man? You don't have to become a meteorologist to understand hardiness zones

The U.S. Department of Agriculture (USDA) created a simple way to help you choose plants for your garden.

It’s called the “USDA Plant Hardiness Zone Map.”

Basically, they’ve assigned a zone to where you live. Your zone is based on the coldest temperatures that are expected in your area.

As long as you choose plants that match your zone, your plants should be strong enough to survive winter temperatures in your area.

The opportune word here is “should.” Hardiness zones are based on the expected coldest temperatures in your area. However, Mama Nature has been known to push the boundaries of coldest temps — like the arctic blast that swept much of the U.S. in February 2021. Plus, there are other factors that can come into play on whether your plants survive winter in the West. The key takeaway? While plant hardiness zones are helpful, they aren’t perfect.

Let’s look at the USDA Plant Hardiness Zone Map

USDA Plant Hardiness Zone Map for United States

You may notice that the coastlines (in oranges and yellows) tend to have warmer winters than the upper-central portion of the United States (in greens, blues and purples).

That’s because the oceans help moderate winter temperatures.

In the Rocky Mountain region of the country, we have a WIDE range of plant hardiness zones. It depends on where you live.

Alpine flowers in the Rocky Mountains can withstand colder winter temperatures. They have lower plant hardiness zones.

You can find your plant hardiness zone on the USDA website

Okay, you’ve looked up your zone number…

Now what the heck are you supposed to do with it?

When you go to buy flowers, look for the zones on the plant tags (tucked in the containers).

If you want your plants to come back next year, pick flowers that match YOUR zone number.

For example, let’s say you live in Zone 5

You see this red fountain grass (below) at the store, and you’d love to plant it in your garden. The plant tag says it’s “annual except in zones 9-11.”

Example of plant hardiness zones on a plant tag

This plant tag is telling you that this grass will likely only survive winter temperatures in Zones 9-11.

Because you are in Zone 5, this plant will look great in your garden for one summer, but it should NOT come back next year. It isn’t winter hardy where you live.

Let’s look at another example

You like the look of the plant below called Red Birds in a Tree. (By the way, this is one of my favorite plants in my garden. My neighbors always ask about it, and the hummingbirds LOVE it!)

The plant tag for this flower says, “Zones 3-9.” Do you see the zones below?

This plant tag shows USDA plant hardiness zones 3-9.

In our example, your garden is in Zone 5, so this plant SHOULD return next year. It should come back in any of the Zones 3-9.

Use your zone to be a smarter plant shopper

When you buy plants that you want to return every year:

  • Don’t assume that the plants at the store are right for where you live.
  • Check the plant tags to make sure their plant hardiness zones match yours.
  • If you’re buying plants online, look for each plant’s hardiness zone in the online description of the plant.

If you pick a plant that doesn’t match your zone, you may find yourself a replacing dead plant next year!

While your plant hardiness zone is helpful, it’s only ONE part of choosing the right flowers for your western garden

Remember that your plant hardiness zone is like your jean size.

When you’re buying jeans, the size is important, yes.

But you probably care about other things too — like the the length, fit and color.

If you’re 5’3′, tall jeans are going to create unnecessary work for you.

And we do not want unnecessary work!

Size is one factor in choosing jeans, just like plant hardiness zones are only one factor in choosing plants

In your western garden, you also want to know:

  • How much water your plants need (can they tolerate semi-arid conditions and drought?)
  • How well your plants can handle intense sunlight (at elevation, we’re closer to the sun, so our sunlight is tougher on plants)
  • Your plants’ tolerance to things like hail and wind
  • What kind of soil the plants like
  • And more

Here’s an example of what can happen if you only think about your plant hardiness zone.

Again, let’s say you live in Zone 5.

If you ONLY consider your plant hardiness zone when choosing flowers, you may find yourself planting the same flowers that thrive in humid, rainy, coastal Maine.

Maine has the same plant hardiness zone as the Front Range of Colorado, so consider more factors than just zones when choosing plants!

Not the best idea for your semi-arid garden in Colorado or Utah, right?

It’s helpful to choose flower plants that fit your zone, but know that your zone is only one part of finding the best flowers for your western garden.

Related tips that may interest you:

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Ann from Go West Gardener with her flowerpots and garden

Hey there, I'm Ann

I’m a Certified Colorado Gardener, dog mama and Midwesterner-turned-Colorado girl. I help budding gardeners in the intermountain west get more confident with flower gardening, so you can create an outdoor space you love. More about Ann >>

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