Growing Zones for Raised Bed Gardens
Container Gardening (such as a Window Box or Deck Planter) is slightly different than growing plants in the ground…which is what the Growing Zone Maps are meant to do. The basic environmental issues are similar but the size and location will vary.
Information for this post is from the 2012 USDA Plant Hardiness Zone Map. Your tax dollars at work by the Agricultural Research Service, U.S. Department of Agriculture. See link at bottom of page
The USDA map is the one most gardeners in the eastern United States rely on, and the one that most national garden magazines, catalogs, books, and many nurseries currently use. This map divides North America into 11 separate zones. Each zone is 10°F warmer (or colder) in an average winter than the adjacent zone.
Check out your growing zone by entering your Zip code at this USDA website (cut and paste in your browser): http://planthardiness.ars.usda.gov
Other Growing Factors
Many other environmental factors, in addition to hardiness zones, contribute to the success or failure of plants. Wind, soil type, soil moisture, humidity, pollution, snow, and winter sunshine can greatly affect the survival of plants. The way plants are placed in the landscape, how they are planted, and their size and health might also influence their survival. Certainly the type of container they are in plays an important factor in successful gardening.
Light: To thrive, plants need to be planted where they will receive the proper amount of light. For example, plants that require partial shade that are at the limits of hardiness in your area might be injured by too much sun during the winter because it might cause rapid changes in the plant’s temperature.
Soil moisture: Plants have different requirements for soil moisture, and this might vary seasonally. Plants that might otherwise be hardy in your zone might be injured if soil moisture is too low in late autumn and they enter dormancy while suffering moisture stress.
Temperature: Plants grow best within a range of optimum temperatures, both cold and hot. That range may be wide for some varieties and species but narrow for others.
Duration of exposure to cold: Many plants that can survive a short period of exposure to cold may not tolerate longer periods of cold weather.
Humidity: High relative humidity limits cold damage by reducing moisture loss from leaves, branches, and buds. Cold injury can be more severe if the humidity is low, especially for evergreens.