Monday, March 10, 2008

Taking a look at the world’s plant hardiness zone maps

Every part of the world has its own hardiness zones, and most maps are set up the same way. The USDA Plant Hardiness Zone Map, for example, is a color-coded or shaded map, sometimes accompanied by a chart that expresses the same information. This book displays the map in the color section, and you can also see the map (and others) in many places after you become tuned in to it — a poster tacked up on the wall at your local garden center, the back flyleaf of gardening books, in the back pages of most garden magazines, or tucked into the interior of your favorite gardening catalog.

You can also access it online at www.usna.usda.gov/Hardzone/ushzmap. The United States Department of Agriculture published, and has occasionally modified and updated, this hardiness zone map of North America. The most recent map, based on climate data gathered at National Weather Service stations throughout the U.S. and by weather stations throughout Canada and Mexico, came out in 1990. You can find 11 zones marking the average lowest winter temperatures, with Zones 2–10 divided into subzones. Canada’s plant hardiness zone map, suited for Canada’s colder climate, shows nine zones, based on average climatic conditions and altitude of each area. The harshest zone is 0, and the mildest is 8. In addition, the major zones are further divided into subzones. For example, Zone 4 splits into 4a and 4b, where zone a is slightly colder than zone b. You can see Canada’s map at atlas.nrcan. gc.ca/site/english/maps/environment/land/planthardi.

The Hardiness Zone Map of Europe presents a general overview of the European continent and can be broken down further into each European nation and the zones within it. You can see this map online at www.uk. gardenweb.com/forums/zones/hze.

China’s plant hardiness zone map covers arguably largest and most varied gardening spots in the world. You can view it at www.backyardgardener. com/zone/china.

Plant hardiness zone maps aren’t limited to just the Northern Hemisphere of the Earth! You can find online maps for South America and Africa as well. And the Australian government has established a series of maps that many Australian gardeners use to gauge not only planting zones and climates but also rainfall. To view the plant hardiness zone map of Australia, go to www. anbg.gov.au/hort.research/zones. To see Australia’s climate zone maps, visit www.bom.gov.au/climate/austmaps. Traveler beware: If you buy a plant marked as perennial or hardy in the deep Southern USA or California and you live in a chilly northern region, the plant may be labeled such only for the area where it’s sold.

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