When selecting plants for your garden, you’ll want to consider the plant’s hardiness zone. Hardiness zones are based on the annual average minimum temperatures that occur in a certain area. The 2012 USDA Plant Hardiness Zone Map is based on the annual average minimum winter temperature, divided into 10-degree Fahrenheit zones. These zones are critical to a gardener’s success, as they provide vital information such as where a plant is known to grow well, as well as frost dates. Learn more about garden zones and how this information could make a difference in your garden.
Purpose of Garden Zones
Not all plants are able to take the sweltering summer heat or blistering cold temperatures. To prevent wasted time, money and effort, many gardeners refer to gardening zones as a way to compare their garden climate with the climate where a plant is known to grow well. This map can often be found on the back of seed packets or online.
If you want a perennial, shrub or tree to thrive in your climate and grow back year after year, the plant must be able to tolerate the weather conditions in your area. While garden zone maps are not exact, they are an excellent estimate to help you determine if a plant will survive the winter in your climate. However, zones are not the only factor to consider when determining whether or not a plant will survive. Day length, rainfall, soil types, humidity, heat, and wind also factor in.
Number of Garden Zones
North America is divided into 13 hardiness zones on the USDA plant hardiness map. The coldest is Zone 1, while the warmest is Zone 13. When you purchase a plant, it will usually have a range of numbers, such as Zones 1 through 3. This means that the plant is usually able to survive when growing in one of those zones. When a plant has no number at all, it usually means that it’s an annual and can only be used for one growing season.
Problems in the West
Due to the flat terrain, using zones to determine the best plants for gardening in the east is highly effective. However, some problems can occur when using zones in the west, due to precipitation and elevation. As various weather conditions push in from the Pacific Ocean, they often become drier and less humid as they move over mountain ranges, which can make it difficult to determine growing climates.
Importance of Frost Dates
Knowing the frost dates in your climate is critical when properly caring for your plants. When planting annuals, the final frost date will indicate that it’s now safe to plant the annuals in the ground. If you’ve planted non-hardy or tropical plants outdoors, the first frost date will let you know that it’s time to bring those delicate plants indoors for the winter. It’s important to keep these frost dates in mind during the spring and fall to ensure that your plants last year-round.