Zones

There are several zones systems un use in the USA. Two are rated on average
minimum winter temperatures: The USDA and the Arnold Arboretum. At one time
there was some difference between maps of the two but the one from the
Arnold Arb. has been modified and they are now essentually the same, with
the USDA being the most frequently used.. you will still need to be careful
with the older books.

Recently (like in the past couple of years) the American Horticultural
Society published the AHS Heat Zone system that is based on average number
of days a year that the temperature is above 86 F. The reason for this is
that the USDA Winter Hardiness are insufficient here in the South... Summer
being the leading season of loss. There was never any intent to replace the
USDA winter zone system. Several scientists that I know challenge the AHS
system, but it is a start...

Then of course there is the Sunset system. Published by Sunset Press, it
has been the dominant system in the Western States with yet a different
climate that the rest of us. The main problems with it is complexity and
that it is proprietary to a commercial publisher who have copyright issues
at heart. Details about the methodology are trade secrets.

And then there is the Bailey's Ecoregion system designed for the ecologist
and not the gardener! You want details, let me know.

The USA is a big country, with lots of climates. No one system as currently
divised is sufficient. To keep it simple, maps are also simplified and
microclimates can make a big difference. All the systems are simply
languages that allow gardener's to communicate better.. or at least they
are supposed to...

Now if you REALLY want to get confused, try understanding all the system in
use in other countries! (Hey big boy: I've got this lovely collection of
maps... snicker, snicker)

The perennial ;-) nature of these questions remind my that I need to get my
rear in gear and get the Garden Climate webpage up....

Take care.

Beth Matney <bmatney@mail.snider.net)
central Arkansas USDA zone 7b (min.temp 5F)
AHS zone 8 (90-120 days > 86F)
Sunset zone 33
Koppen climate group Cf
Bailey's Ecoregions 231/M231 -
  Subtropical Division
  Southeastern Mixed Forest Province/Ouachita Mixed Forest

---------------------------------------------------------------------
To sign-off this list, send email to majordomo@mallorn.com with the
message text UNSUBSCRIBE PERENNIALS
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index