Amorphophallus: Hardiness Zones

So what's wrong with plant hardiness zones?
Well, just think about this: The average minimum temperature is not the only factor in figuring out whether a plant will survive in your garden. Soil types, rainfall, daytime temperatures, day length, wind, humidity and heat also play their roles. For example, although both Austin, Texas and Portland, Oregon are in the same zone (8), the local climates are dramatically different. Even within a city, a street, or a spot protected by a warm wall in your own garden, there may be microclimates that affect how plants grow. The zones are a good starting point, but you still need to determine for yourself what will and won't work in your garden.

How many zones are there?
The USDA plant hardiness map divides North America into 11 hardiness zones. Zone 1 is the coldest; zone 11 is the warmest, a tropical area found only in Hawaii and southernmost Florida. In between, the zones follow a fairly predictable pattern across the continent, though a closer look will reveal scattered patterns of variations. Generally, the colder zones are found at higher latitudes and higher elevations.

Applying zone references
Plant encyclopedias may refer simply, for example, to "Zone 6," which generally means that the plant is hardy to that zone (and will endure winters there), and generally can withstand all the warmer zones below. More detailed information may indicate a range of zones (i.e., "Zones 4-9"), which means the plant will only grow in those zones, and will not tolerate the colder and warmer extremes outside them. But remember, zones are only a guide. You may find microclimates that allow you to grow more than the books say you can; by the same token, you may find to your dismay that some precious plant -- one that's "supposed" to be hardy

Sunset Zones versus USDA Zones (source- http://www.backyardgardener.com/zone/ )

Gardeners in the western United States sometimes are confused when confronted with the 11 Hardiness Zones created by the USDA (United States Department of Agriculture), because they are used to a 24-zone climate system created 40 years ago by Sunset Magazine. The Sunset zone maps, which cover 13 Western states, are much more precise than the USDA's, since they factor in not only winter minimum temperatures, but also summer highs, lengths of growing seasons, humidity, and rainfall patterns to provide a more accurate picture of what will grow there.

If you live in the western U.S., you'll find that nurseries, garden centers, and other western gardeners usually refer to the Sunset climate zones rather than the USDA plant hardiness zones. In fact, the Sunset zones and maps are what are listed for each plant in Sunset's Western Garden Book and Western Garden CD-ROM, which are considered the standard gardening references in the West.

However, the USDA zones are still of importance to western gardeners, since the USDA zones are used in the rest of the country. When you order plants from catalogs or read general garden books, you need to know your USDA zone in order to be able to interpret references correctly. To determine your USDA zone, use the links above.

If you live outside North America
You can roughly translate the USDA hardiness zones by finding out how low your area's temperatures can reach, and then use the chart below to find your corresponding zone.

Zone 1: below -46 C (below -50 F)
Zone 2: -46 to -40 C (-50 to -40 F)
Zone 3: -40 to -34 C (-40 to -30 F)
Zone 4: -34 to -29 C (-30 to -20 F)
Zone 5: -29 to -23 C (-20 to -10 F)
Zone 6: -23 to -18 C (-10 to 0 F)
Zone 7: -18 to -12 C (0 to 10 F)
Zone 8: -12 to -7 C (10 to 20 F)
Zone 9: -7 to -1 C (20 to 30 F)
Zone 10: -1 to 4 C (30 to 40 F)
Zone 11: above 4 C (above 40 F)