Due to a long growing season and mild winters, the North Carolina climate is ideal for gardening. Since the terrain ranges from mountains to coastline, average annual temperatures vary across the state. If you're not sure what plants will thrive in your particular North Carolina location, the USDA Plant Hardiness Scale is a helpful tool to reference.
USDA Plant Hardiness Zones
The Plant Hardiness Scale is a system developed by the United States Department of Agriculture (USDA) that outlines climate conditions to help determine what plants will thrive and survive in a specific area. The map divides North America into 13 individual zones—each zone is delineated by an annual extreme minimum temperature and separated by a difference of five degrees.
For example, the city of Charlotte, North Carolina, is split into two zones: 7a and 7b. In zone 7a, temperatures may dip as low as 5 degrees Fahrenheit (negative 15 degrees Celsius) on the coldest days of the year. The neighboring zone 7b experiences lows dropping to 10 degrees Fahrenheit (negative 12.2 degrees Celsius) in the winter.
Once you know your areas hardiness zone, you can then select plants that grow best in your location. Most plants and seed packages will have their zones marked on the label or planting information cards.
While the USDA scale is based on past weather records, it's still merely an estimation, as weather is unpredictable and constantly changing. It's certainly possible to have an unusually mild or cold winter, so referencing the map when purchasing plants remains an educated guess. If you want to lessen the risk of your perennial plants dying over the winter, you can try selecting varieties that are hardy in a zone or two above your location.
North Carolina USDA Plant Hardiness Zones
North Carolina is comprised of five hardiness zones: 6a, 6b, 7a, 7b, and 8a. The areas that experience the lowest temperatures (zones 6a and 6b) are located in the western part of the state, as it features a significantly higher elevation than the coastline. Mountain cities in these zones, like Asheville, will see higher occurrences of freezing and snow in the winter and have a slightly shorter growing season.
The central parts of the state are comprised of zone 7a and 7b, and freezing is less common than it is in the mountainous areas. You can grow most plants in these zones with the exception of tropical varieties.
The most southern coastal areas of the state fall into zone 8a on the USDA Plant Hardiness Scale, and warmer weather plants and trees (like citrus) can survive outside as long as they are protected on the coldest days.
In North Carolina, the growing season ranges from late March to early November; rain falls year-round in a range of 37 to 50 inches annually, and winter lows are between 15 and negative 5 degrees Fahrenheit. The state does experience some intense humidity, especially in the southernmost border and coast.
North Carolina Plant Pests
Pests are another factor to consider when determining whether or not a plant will survive in a specific area. The USDA Plant Hardiness Zone map is strictly based on temperatures—it doesn't take into account any potential pests, which are a common problem in the Southern portion of the United States. If you want to know more about which pests to look out for in your specific area of North Carolina (as well as updates on periodic pest outbreaks), you can find more information at The North Carolina State University Plant Disease and Insect Clinic.