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The u.s.d.a. Plant hardiness zone
map
The United States Department of
Agriculture (U.S.D.A.) has established Plant Hardiness Zones for the USA,
Canada and Mexico based on analysis of the range of average annual minimum
temperatures experienced in each area as recorded during the period 1974
through 1986. According to the U.S.D.A. temperature data book issued by
Meteorological Evaluation Services Co. Inc. of Amityville, NY, "the
purpose of this data listing is to enable one to determine the hardiness
zone of any given city, town or location used in the map analysis as well
as to provide the annual minimum temperatures over the 10-plus years for
comparison with future weather."
When planning a garden, consider your local climate and the established
"hardiness rating" of various plants you have in mind. Some plants cannot
handle severe winters; others wither in heat; still others, such as many
spring-flowering bulbs, need a cold period to stimulate growth cycles.
Look at plant labels, bulb packaging, catalogues and reference books for
the hardiness ratings of individual plants.
Plant spring-flowering bulbs in your area 6 weeks before the ground
freezes.
Average annual minimum
temperatures for
each zone |
Average appropriate fall planting time
for flower
bulbs in each zone |
| Zone 1: |
below -50°F |
by early September |
| Zone 2: |
-50°F to -40°F |
by early September |
| Zone 3: |
-40°F to -30°F |
by September |
| Zone 4: |
-30°F to -20°F |
by late September to early October |
| Zone 5: |
-20°F to -10°F |
by late September to early October |
| Zone 6: |
-10°F to 0°F |
by mid-October |
| Zone 7: |
0°F to 10°F |
by early November |
| Zone 8: |
10°F to 20°F |
by early November |
| Zone 9: |
20°F to 30°F |
by early December
(some chilling required) |
| Zone 10: |
30°F to 40°F |
by mid-December
(some chilling required) |
| Zone 11: |
above 40°F |
by late December
(some chilling
required) |
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