In the United States, the United States Department of Agriculture defines numerical growing regions based on winter and summer temperature averages and all trees, shrubs and seeds are labeled according to these growing regions. Across the Southern United States, the regions are numerically higher, indicating longer summer growing seasons and winters with few nights below freezing. The upper Midwest, including parts of Minnesota and Wisconsin, are numerically lowest with the shortest growing season and historically harshest winters.
To know if know a particular tree or shrub can be grown in your region, check the listed USDA growing region number against the numerical hardiness of the tree or shrub. Most trees and shrubs available for sale include the ideal growing regions for them on the plant tag or web description. A complete view of the USDA growing region map is available at ArborDay.org.
Many trees and shrubs can grow in any region with sufficient soil quality, sunlight and water. Some trees, such as many varieties of fig trees, grow differently depending on the growing region. In warmer regions, such as region seven or eight, fig trees are evergreen trees with multiple annual crops of fruit. In cooler regions, the tree adjusts to one crop of fruit and drops its leaves in the winter.