Understanding USDA Plant Hardiness Zones: What You Need to Know for Northern Colorado

If you want your Colorado garden to thrive year after year, understanding USDA Plant Hardiness Zones is essential. These zones are your guide to selecting trees, shrubs, and perennials that will survive local winters. While some plants may flourish in places like Georgia or California, they may not make it through a single Northern Colorado winter. With Colorado’s diverse elevations and microclimates, knowing your zone can make or break your gardening success.

Click the image for access to an interactive map of the USDA Hardiness Zones and learn which zone you are in today! Use your zip code to find which plant hardiness zone you are located in.

What Are USDA Plant Hardiness Zones?

USDA Hardiness Zones are geographic areas defined by the average annual extreme minimum temperature. The United States is divided into 13 zones, with each zone differing by 10°F. For even more accuracy, each zone is split into "a" and "b" subzones. For example, Zone 5b has average lows between -10°F and -15°F, while Zone 6a ranges from -5°F to -10°F.

These zones help gardeners determine which plants are most likely to thrive based on their cold tolerance. A plant labeled hardy to Zone 5 will likely survive in areas that don't dip below -20°F.

The 2023 USDA Zone Map Update

The USDA released an updated Plant Hardiness Zone Map in 2023, offering more accurate temperature data than ever before. Thanks to advances in mapping and temperature tracking, gardeners now have a more precise guide for selecting climate-appropriate plants.

Northern Colorado's USDA Zones (2023)

• Fort Collins: Zone 5b, with average lows of -10°F to -15°F

• Loveland/Windsor: Zones 5b to 6a

• Denver: Generally Zone 6a

• Summit County and mountain towns: Zones 4b to 5a, depending on elevation

  
  

Even within a single town, elevation and microclimates can shift your zone slightly, so it's always smart to double-check using your zip code on the USDA’s interactive map.

Do Hardiness Zones Really Matter?

You might be asking, does it really matter if I am in Hardiness Zone 6, but I want to buy a plant that is specific to Hardiness Zone 7? Many people may be tempted to buy a plant outside of their zone because they like the way it looks or the colors it displays, and then get frustrated and disheartened when the plant does not survive or when it loses all of the beautiful features that drew you to the plant in the first place. So, the answer to this question is yes, it does matter!

All plants present a lovely display unique to their variety, and often this display, whether it is vibrant color, beautiful flowers, deep green foliage, etc., is dependent on the climate and the growing environment which the plant is in. The 10-degree difference in zones, though it may seem insignificant, is easily enough to affect the way your plant grows, and cold temperatures can easily cause irreparable damage. If the plant does not get the right amount of sun and warmth, it will lose its color. Or if a plant gets too cold, it may not flower. That is why the Hardiness Zones were developed– to help people know which plants will grow best in which climates.

When it comes to subzones, most plants are usually able to adapt. Some plants may not even be labeled so specifically that subzone is mentioned. So, if you know you are in zone 9a and find a plant that only says it is suited to zone 9, the chances that your plant will survive are very high. Even if the plant in question is labeled as suited to zone 9b, most plants will likely be fine once it has become adapted to the area. Overall, though, it is always best to not push the limits of any plant when it comes to planting it somewhere outside of the area it is best suited for, as climatic conditions may not be suitable for the growing needs of the trees, shrubs, or perennials you have in mind.

So, while buying a plant that is marked for Zone 8 when you live in Zone 5 (or any zone that is warmer than the one you are in) may not result in the immediate death of your plant, it definitely will affect the health of the plant, and therefore the plant will likely lack many of the qualities that made it so beautiful and intriguing. You can, however, plant something that is hardy to zone 3 in zone 5. This is because a zone 3 plant will be able to withstand temperatures much colder than zone 5 will ever experience, so the plant will be fine. So, in most situations, you can plant something from a colder zone in a warmer zone, but you cannot plant something from a warmer zone in a colder zone, as a warm-weather plant will not be able to withstand the extreme temperatures of a hardiness zone that is colder than the one they are rated for.

How To Read a Plant Hardiness Zone Map in the USA

Reading a USDA hardiness zone map is really very simple. If you do a Google search, the first result will likely be a map of the designated hardiness zones with a list of USDA zones on one side, each with individual colors that are correlated to each USDA zone. As can be seen in the zone map below, the map of the United States is colored based on the average annual minimum temperature of locations across the country.

No matter where you live, you can use the USDA Plant Hardiness Zone Map to find your zone based on color. Many online maps also let you enter your zip code for an exact match. Here in Fort Collins, Colorado, we are in Zone 5b, where winter temperatures typically drop between -10°F and -15°F.

Our Advice: Stick to Your Zone

Choosing plants suited to your USDA hardiness zone is the first step toward a successful, low-maintenance garden. At Bath Garden Center in Fort Collins, we make it easy—we only stock plants that will thrive in Northern Colorado’s unique climate. Whether you're a beginner or a seasoned gardener, our team is happy to help you select zone-appropriate plants and avoid the disappointment of winter losses.

Learn More About USDA Hardiness Zones

If you have any concerns about specific plants or questions about what will grow in your area, please reach out to us through our website! We are here to help with all your questions and are happy to provide you with the important information you need to determine which plants to grow in our region. Also, here at Bath Garden Center in Fort Collins, we only sell what will grow and thrive in the area! So, if you are purchasing plants for your yard and you live nearby, swing by for a visit. You won’t have to worry about whether your plant will survive, since all our plants are hand-picked and specific to our climate here in Northern Colorado. We look forward to seeing you and helping you pick out the perfect plants for your yard!