About Plant Hardiness Zones
Because growing requirements for each plant vary, you can use the hardiness zone map as a general guide for which plants will survive temperatures in your region. It will help you to determine which plants may be suitable for your particular site. Remember that your site has micro-climates and so this is important to consider where temperature is concerned.
The first hardiness zone map was produced in 1927 and has been continually refined. Scientists built databases recording the highest and lowest mean temperatures throughout the regions of the United States. In 1960 the USDA published it’s first hardiness zone map and they are continually gathering information on growing seasons and weather. The latest USDA map was produced in 1990, (based on weather records from 1974-1986). It was the standard for measuring growing seasons throughout the United States until 2006.
Since then, extensive changes in the world climate have inspired the National Arbor Day Foundation to underwrite a thorough update of the hardiness zone map. Using data collected from 5,000 National Climatic Data Center cooperative stations across the continental United States, they have provided the 2006 Hardiness Zone Map under a Creative Commons License.
Plant Hardiness Zones provide one factor in your plant choices. Other factors to consider are rainfall, hours of daylight, wind, humidity, and rainfall, among others. Your own town, block, or yard will have it’s own microclimate. How plants grow will be affected by if one area or another is wetter, hotter drier, or colder, etc. This zone map is a good beginning, and from there you can narrow your choices to meet your site specific conditions.
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 2.5 License.