zone maps

2012 Zone Hardiness Map

Every few years the US Department of Agriculture revises their Plant Hardiness Zone maps. The maps are an invaluable resource to gardeners and nurseries, and are a reliable guide for understanding what plants are able to overwinter in a particular area of the country. Its folly to attempt to create a garden of plants that won't thrive in your neighborhood. The maps are revised, and provide anecdotal evidence to non-believers, that winter temperatures in the US are on the rise.

When I began gardening in the early 90's all of Missouri was situated in USDA Zone 5, which meant that winter low temperatures would hit -10 degree Fahrenheit (-23 C). Today, the same garden sits in Zone 6, with winter low temps 5-10 degree warmer. Since the 1990's map, zone changes have inched northwards 10 miles per year.

I have always wanted a southern garden but I like it here and and am unwilling to move. However, if the current rate of change continues, the Fashionista can spend her dotage with a New Orleans garden without having to leave home.

The Arbor Day Foundation has a wonderful interactive map demonstrating the changes here.

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