The United States Department of Agriculture Plant Hardiness Zone Map divides North America into 11 zones based on average minimum winter temperatures, with Zone 1 being the coldest and Zone 11 the warmest. Each zone is further divided into sections that represent five-degree differences within each ten-degree zone.
This map should only be used as a general guideline, since the lines of separation between zones are not as clear-cut as they appear. Plants recommended for one zone might do well in the southern part of the adjoining colder zone, as well as in the neighboring warmer zone. Factors such as altitude, exposure to wind, proximity to a large body of water, and amount of available sunlight also contribute to a plant's winter hardiness. Because snow cover insulates plants, winters with little or no snow tend to be more damaging to marginally hardy varieties. Also note that the indicated temperatures are average minimums -- some winters will be colder and others warmer.
Your zone is just one factor you must consider when choosing plants for your garden. You must also determine the light conditions of your garden, taking into consideration the position of buildings or large trees and shrubs. Keep reading to learn more about assessing garden light conditions.
Looking for more information about gardening? Try these:
- How to Start a Garden: Find out how to get your garden started.
- Planting a Garden: Once the planning is done and the soil is ready, the next step is planting your flowers or vegetables.
- Annual Flowers: Learn about annual flowers, which continue to bloom throughout the growing season.
- Perennial Flowers: Find out about perennial flowers, which return to grace your garden year after year.
- Gardening: Learn the basics of successful gardening.