WASHINGTON, U.S.A. - Global warming is hitting not just home, but garden. The colour-coded map of planting zones often seen on the back of seed packets is being updated by the government, illustrating a hotter 21st century.It's the first time since 1990 that the US Department of Agriculture has revised the official guide for the nation's 80 million gardeners, and much has changed. Nearly entire states, such as Ohio, Nebraska and Texas, are in warmer zones.
The new guide, unveiled on Wednesday at the National Arboretum, arrives just as many home gardeners are receiving their seed catalogues and dreaming of lush flower beds in the spring.
It reflects a new reality: The coldest day of the year isn't as cold as it used to be, so some plants and trees can now survive farther north. "People who grow plants are well aware of the fact that temperatures have gotten more mild throughout the year, particularly in the wintertime," said Boston University biology professor Richard Primack. "There's a lot of things you can grow now that you couldn't grow before."- The giant fig tree in his suburban Boston yard stands as an example: "People don't think of figs as a crop you can grow in the Boston area. You can do it now."
- The new guide also uses better weather data and offers more interactive technology. For example, gardeners using the online version can enter their ZIP code and get the exact average coldest temperature.
Also, for the first time, calculations include more detailed factors such as prevailing winds, the presence of nearby bodies of water, the slope of the land, and the way cities are hotter than suburbs and rural areas.The map carves up the US into 26 zones based on five-degree temperature increments.
The old 1990 map mentions 34 US cities in its key. On the 2012 map, 18 of those, including Honolulu, St. Louis, Des Moines, Iowa, St. Paul, Minn., and even Fairbanks, Alaska, are in newer, warmer zones.
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