Hi im new to all of this and have recieve a lot of great information. I
have a question, I notice you all talk about zones , how can i tell
what zone is what area ? Im in Washington, what zone is that ?
The problem with the USDA zones is that they are based entirely on the
amount of frost free days and not other climate factors. Thus, most of
Seattle is in a USDA zone that corresponds to Atlanta, I believe, even
though I think our climates are very different.
For gardeners in the Western US, I think Sunset zones are more useful. If
you're in Puget Sound, you're probably in Zone 4 or 5 in the Sunset system.
From their website (which I don't think you can get into unless you're a
subscriber, so I will reproduce rather than hyperlink):
Zone 4. Many people know this zone for the miles of tulips in the Skagit
Valley. In fact, this area has more spring bulbs under cultivation than all
On Sun, 27 Feb 2005 17:06:28 -0800, "Claire Petersky"
The USDA zones are based on the average annual minimum temperatures, not on the
number of frost-free days. It is helpful if used as intended, but useless in any
other application. There are also other problems with this system. The latest
revision was based on data accumulated from some of the warmest winters on
record, and the previous map was based on data from some of the coldest winters
we've had. Statistical adjustments would help somewhat, but that appears to be
out of the reach of the USDA bureaucrats.
Very true. Sunset began their system with detailed information on southern
California, and expanded it to include the rest of the west coast. They've also
published a national guide, but it is less detailed, less accurate, and much
There is at least one other 'zone' system. The American Horticultural Society
has published a Heat Zone guide. It is based on the fact that most common garden
plants suffer cellular protein damage at 86 degrees F. The zones are determined
by how many days (on average) the highs reach or exceed 86F. Coastal Washington
state is in zones 2 and 3 and has between 1 and 14 days at or above 86F.
'Hotlanta' is in zone 8 or 9 (the map in the book is too small for me to be more
certain), with between 90 and 150 days at or above 86F. Both areas are in USDA
Zone 8 because their average annual minimum temps are between 10F and 20F. The
difference in heat accounts for much of the difference between the two areas.
But neither the USDA nor the AHS consider other important factors, such as
amount and timing of rainfall, potential for drought, intensity and timing and
duration of winds, amount of sunshine, chilling hours, etc. There was an
announcement a year or two ago that labels on plants in most of the country
would have zone information from both the USDA and the AHS maps, but I haven't
seen that yet. I'd really like it if Sunset would do as thorough a job on the
whole country as they have on the west coast states, but I do appreciate that it
would be an enormous undertaking and might not be as popular nor as profitable,
at least not initially.
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