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)


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 in
your zone -- finds its way to plant heaven instead.

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