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New USDA zone map

Tony Avent of Plant Delights had a part in the construction of the
new USDA zone map. Here he describes some of its details to John Bryan
(author of the bulb book):

Subject: Re: [pbs] Climate zones
Date: Fri, 28 Oct 2005 15:33:08 -0400
From: Tony Avent <tony@plantdelights.com>
To: Pacific Bulb Society <pbs@lists.ibiblio.org>


	 Work on the new USDA map began on August 18, 2004. In 2003, a draft
version was released by the American Horticulture Society which caused
quite an uproar in the horticultural community. This revision would have
done away with the "a" and "b" zone designations and would have been based
on a fifteen year sample (1986-2001) of climatic data. By using a 15-year
warm period sample, the draft map would have moved Chicago into zone 6 and
made other such disastrous errors.

Thanks to the support of Dr. Judy St. John of USDA-ARS, the map revision
was put on hold until input from the stakeholders (government term for
folks most affected by government decisions) could be gathered. The August
18 meeting included representatives from USDA- ARS, the American
Horticulture Society, the American Association of Botanic Gardens and
Arboreta, University Researchers, and representatives of the nursery

The project will consist of two phases. In Phase I, the map will be
reconstructed using the most recent 30 years of average annual extreme
minimum temperatures. The map will also retain the "a and b" designations.
For the first time, the map will include a better breakdown of coastal/lake
effects, urban heat islands, wind patterns, and elevation differences.  Due
to advances in interpolation algorithms, the map will pick up on small
differences that were previously missed.  The map will be made available
on-line where it can be searched both by city and zip code. The on-line map
will be clickable for more detailed climatic data to satisfy what the
research scientists called, "those pointy-head weather nerd types."

Phase II of the project will involve overlay maps for other factors such as
duration of cold, summer heat factors, and possibly air flow patterns. It's
not often that I get excited about a government project, but this will be a
huge improvement for our industry. Thanks both to the USDA-ARS for making
their resources available and for all of the committee members for their
time and input into the process.
Tony Avent
Jim Fisher
Vienna, Virginia USA
38.9 N 77.2 W
USDA Zone 7
Max. 95 F [36 C], Min. 10 F [-12 C]

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