The USDA plant hardiness map is the go-to resource for gardeners, designers, and growers to help them determine which plants will thrive in a specific location. This map uses the average minimum winter temperatures which is then broken down into 10 degree zones and 5 degree half zones. They’re numbered 1-13 and are followed by the letter a or b for the half zones with 1 being the coldest and 13 being the warmest. An updated plant hardiness map was released in November of 2023 which takes rising temperatures into account since its last update in 2012.
In Lake Stevens our zone is considered 8b and the hardiness map has the winter temperatures at 15-20 degrees F. But that doesn’t mean that every plant labeled 8b or lower is going to work in our area. As designers, we have to be keenly aware of our area’s microclimates to ensure we’re choosing plants that will survive both winter and summer conditions and your garden’s own microclimates. Because of this, we use the hardiness map as a guideline rather than a hard and fast rule.
Other things we look at when selecting plants include a location’s elevation, sun/shade exposure, how much rain/snow it gets, wind exposure, building and parking lot locations, and its proximity to water whether that be the sound or a lake or a river. All of these conditions can affect a plants survivability and even one of these conditions can override the hardiness zone. A good example of this is Lake Stevens being in 8b and parts of southern Arizona also being in 8b. A plant that thrives in Arizona most likely won’t do well with all the precipitation that we get in Washington and vice versa. Places may have similar winter temps but all the other environmental factors play into how well a plant will do. If a plant gets planted in the wrong zone, they can drop leaves, not flower or produce seeds, be more susceptible to pests and disease, have stunted growth, or even die which can be frustrating and expensive to deal with.
If you’re just starting out on your gardening journey, the hardiness map is a great place to get your bearings. Your local nurseries should also have a strong knowledge of which plants will work in which locations. Consideration of your hardiness zone along with your specific site conditions, environmental factors, and aesthetic and functional preferences will help you choose the right plant for the right place and will set you up for success in the long run.
To see what zone you’re located in, you can check out the interactive map here.
