Understanding your USDA hardiness zone helps you to know which plants grow well in your area. It only takes a few seconds to figure out what zone you’re in. And it will save you a lot of grief in the long run.
That said, let’s jump right into things. Let’s take a look at some of the more common questions I’ve been getting about plant hardiness zones.
What are USDA plant hardiness zones?
A hardiness zone is a geographically defined area with a specific range of average, annual, extreme, minimum temperature during a 30-year period.
How are USDA plant hardiness zones determined?
Several countries use some form of a plant hardiness zone system. The most widely used system is a system that was first developed in the United States by the United States Department of Agriculture (USDA). Over the years, other plant hardiness rating systems have been developed. But the first plant hardiness rating system was developed in the United States.
The hardiness zone system currently used in the United States is a system developed by the United States Department of Agriculture (USDA). It divides the country into 13 zones (with 26 subdivisions).
Zone | From | To |
0 a | < −65 °F (−53.9 °C) | < −65 °F (−53.9 °C) |
0 b | −65 °F (−53.9 °C) | −60 °F (−51.1 °C) |
1 a | −60 °F (−51.1 °C) | −55 °F (−48.3 °C) |
1 b | −55 °F (−48.3 °C) | −50 °F (−45.6 °C) |
2 a | −50 °F (−45.6 °C) | −45 °F (−42.8 °C) |
2 b | −45 °F (−42.8 °C) | −40 °F (−40 °C) |
3 a | −40 °F (−40 °C) | −35 °F (−37.2 °C) |
3 b | −35 °F (−37.2 °C) | −30 °F (−34.4 °C) |
4 a | −30 °F (−34.4 °C) | −25 °F (−31.7 °C) |
4 b | −25 °F (−31.7 °C) | −20 °F (−28.9 °C) |
5 a | −20 °F (−28.9 °C) | −15 °F (−26.1 °C) |
5 b | −15 °F (−26.1 °C) | −10 °F (−23.3 °C) |
6 a | −10 °F (−23.3 °C) | −5 °F (−20.6 °C) |
6 b | −5 °F (−20.6 °C) | 0 °F (−17.8 °C) |
7 a | 0 °F (−17.8 °C) | 5 °F (−15 °C) |
7 b | 5 °F (−15 °C) | 10 °F (−12.2 °C) |
8 a | 10 °F (−12.2 °C) | 15 °F (−9.4 °C) |
8 b | 15 °F (−9.4 °C) | 20 °F (−6.7 °C) |
9 a | 20 °F (−6.7 °C) | 25 °F (−3.9 °C) |
9 b | 25 °F (−3.9 °C) | 30 °F (−1.1 °C) |
10 a | 30 °F (−1.1 °C) | +35 °F (1.7 °C) |
10 b | +35 °F (1.7 °C) | +40 °F (4.4 °C) |
11 a | +40 °F (4.4 °C) | +45 °F (7.2 °C) |
11 b | +45 °F (7.2 °C) | +50 °F (10 °C) |
12 a | +50 °F (10 °C) | +55 °F (12.8 °C) |
12 b | +55 °F (12.8 °C) | 60 °F (15.6 °C) |
13 a | 60 °F (15.6 °C) | 65 °F (18.3 °C) |
13 b | > 65 °F (18.3 °C) | > 65 °F (18.3 °C) |
So, for example, and using the USDA plant hardiness zone system, a plant may be described as “hardy to zone 7.” Which means that the plant can withstand a minimum temperature of 0 °F (−17.8 °C) to 10 °F (-12.2 °C).
Why are USDA plant hardiness zones important?
USDA plant hardiness zones are important because they provide valuable information to gardeners, landscapers, and agricultural professionals about the types of plants that are most likely to thrive in a given region. By knowing their USDA plant hardiness zone, gardeners can select plants that are adapted to the climate conditions in their area, which can increase the chances of successful plant growth and survival.
Additionally, using USDA plant hardiness zones can help save time and money, as it can prevent gardeners from wasting resources on plants that are unlikely to survive in their region. For example, a gardener in a cold climate zone may not want to invest in a tropical plant that requires warm temperatures to survive.
USDA plant hardiness zones are also used by researchers, plant breeders, and agricultural professionals to develop new plant varieties that are adapted to specific regions. By using the USDA zone map as a reference, they can identify which plants are most likely to thrive in a given region and create new plant varieties that are better suited to local climate conditions.
Overall, USDA plant hardiness zones are an important tool for understanding climate conditions and selecting plants that are adapted to local growing conditions. By using this information, gardeners and landscapers can create more sustainable and productive gardens and landscapes, while also conserving resources and reducing waste.
Can plants survive outside their recommended USDA plant hardiness zone?
Some believe that planting and digging in damp soil is advantageous since it requires less physical effort.
While it is generally recommended to choose plants that are recommended for your USDA plant hardiness zone, it is possible for some plants to survive outside of their recommended zone. This is because there are many other factors that can impact plant survival, such as soil type, sun exposure, rainfall, and wind.
Some plants may be able to survive in a colder or warmer zone if they are provided with optimal growing conditions. For example, a gardener in a colder zone may be able to successfully grow a tropical plant if they provide it with a warm microclimate, such as planting it near a building that absorbs and radiates heat. Similarly, a gardener in a warmer zone may be able to grow a plant that is typically recommended for a cooler zone if they provide it with sufficient shade or water.
However, it is important to note that there are limits to how much a plant can adapt to a different climate zone. Plants that are grown outside of their recommended zone may be more susceptible to stress, disease, and insect damage, which can reduce their overall health and vigor. Additionally, some plants may be able to survive in a different zone for a few seasons, but may not be able to withstand long-term exposure to climate conditions that are significantly different from their natural habitat.
That said, and while it is possible for some plants to survive outside of their recommended USDA plant hardiness zone, it is generally recommended to choose plants that are adapted to your local climate conditions for the best chances of successful growth and survival.
Do USDA plant hardiness zones change over time?
Plants may drown if they are given too much water. Rather than watering your plants each day, you
Yes, USDA plant hardiness zones can change over time due to shifts in temperature patterns caused by climate change. As temperatures rise or fall, the boundaries of the USDA plant hardiness zones can shift, which can impact the types of plants that can grow and survive in a particular region.
In fact, since the first USDA plant hardiness zone map was created in 1960, there have been several updates and revisions to the map as a result of changes in temperature patterns. The most recent update was in 2012, which reflected changes in temperature patterns over the previous 30 years.
It is important to note that while changes in temperature patterns can impact the boundaries of the USDA plant hardiness zones, other factors such as precipitation patterns and extreme weather events can also impact plant survival and growth. That said, it is important to use the USDA zone map in combination with other resources and to be aware of the local climate conditions and microclimates in your area when selecting plants for your garden.
How can I find out what USDA plant hardiness zone I am in?
To find out which plant hardiness zone you are in, you can use the plant hardiness zone map. The United States Department of Agriculture (USDA) has created a map that divides the country into 13 zones based on the average minimum winter temperatures in each area.
To use the USDA plant hardiness zone map, follow these steps:
Go to the USDA plant hardiness zone map website: (https://planthardiness.ars.usda.gov/).
Click on your state or territory on the map to zoom in to your region.
Identify your location on the map and determine which zone it falls into.
I also like sites like https://garden.org/nga/zipzone that allow you quickly find you zone by ZIP code. And it shows some of the changes that have been made to the map, over the years.
Are there limitations to the USDA hardiness zone system?
Yes, there are some limitations to the USDA hardiness zone system, as it is based solely on the average minimum winter temperature in a given region and does not take into account other important climate factors such as the number of frost-free days, precipitation patterns, and extreme weather events.
Some other limitations of the USDA hardiness zone system include:
Microclimates: The USDA zone map does not take into account the variations in temperature and weather conditions within a particular region, such as microclimates. For example, a garden located in a sheltered area or near a body of water may experience milder winter temperatures than the rest of the region.
Long-term climate trends: The USDA hardiness zone map is based on historical weather data, and does not account for long-term climate trends or changes. Climate change is causing shifts in temperature patterns, which may result in plants being able to survive in areas that were previously too cold.
Extreme weather events: The USDA zone map does not take into account extreme weather events such as droughts, floods, and heatwaves, which can have a significant impact on plant survival and growth.
Despite these limitations, the USDA hardiness zone system is still a valuable tool for gardeners, landscapers, and agricultural professionals to help them select plants that are likely to thrive in their region. It is important to use the USDA zone map in combination with other resources and to be aware of the local climate conditions and microclimates in your area.
How can I use USDA plant hardiness zones to choose plants for my garden?
You can use the USDA plant hardiness zones as a guide for selecting plants that are adapted to the climate conditions in your area. Here are some steps to help you choose plants based on your USDA plant hardiness zone:
Determine your USDA plant hardiness zone: Use an online zone map or contact your local cooperative extension office to find out what zone you are in.
Identify plants suitable for your zone: Look for plant information that specifies the recommended USDA plant hardiness zones. Most plant labels, seed packets, and online plant descriptions will indicate the appropriate zones for a particular plant.
Consider other factors: While USDA plant hardiness zones are an important guide for selecting plants, other factors such as soil type, sun exposure, and rainfall should also be considered. Be sure to choose plants that are adapted to the specific growing conditions in your garden.
Experiment with microclimates: If you are interested in growing plants outside of your recommended USDA plant hardiness zone, try creating a warm or cool microclimate in your garden. For example, planting next to a south-facing wall can create a warm microclimate that may be suitable for some plants.
Where can I find information about plants that are compatible with my hardiness zone?
My favorite resource: Home Depot.
You might be skeptical, but hear me out before you dismiss Home Depot as one of the best online plant nurseries. In fact, their selection of plants online is much greater than what you’ll find in their stores, including some of the newest 2023 perennials and shrubs from Proven Winners and the Southern Living Plant Collection. You can even find plants that you might not be able to find anywhere else.
Home Depot’s website offers a wide range of plants for sale, including fruit trees, annuals, vegetables, roses, and seeds, in addition to perennials. Many buyers have said that when they’ve ordered plants online from them, they’ve received their order within a day or two, and the plants have been well packaged and in excellent condition. Plus, if you do encounter any problems, you can easily return the plants to any Home Depot store.
If you’re unsure about which plant to choose, their website has filters that allow you to select your gardening zone and specific plant characteristics, such as flower color, evergreen or deciduous leaves, “attracts butterflies” or “deer resistant.” This makes it much easier to find the right plant for your specific growing conditions.
To get started, simply go to:
and select the circle for your gardening zone, and then browse through the selection of plants available.
Conclusion
In conclusion, understanding your USDA plant hardiness zone is a critical first step in successful gardening. By selecting plants that are adapted to your climate, you can ensure that your landscape will thrive and provide the beauty and diversity you desire. However, it is important to keep in mind that the hardiness zone system is not a perfect predictor of plant survival, and other factors should also be considered when selecting plants. However, by using the USDA hardiness zone map as a guide and consulting with local experts and resources, you can create a landscape that is well-suited to your specific climate and location.