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  What are the criteria for "Zones"?
From: "Ron Iles" roniles at eircom.net> on 2002.05.21 at 16:44:50(8840)
Please can someone explain what criteria are used for
"Zones"? With a range of rarely freezing to rarely touching 80F,
what "Zone" is West Cork Ireland? This is 20F too low in summer
& 30-40F too low in winter for growing Spaths outside, especially with sea
winds etc.
From: "Hawaii Tropical Botanical Garden" htbg at ilhawaii.net> on 2002.05.21 at 19:46:58(8841)
Hi Ron,

Climate zones are also called hardiness zones and generally refer to the
degree of cold, without much reference to degree of warmth. Frustrating for
those of us in warmer climes, there is very little information on cold
REQUIREMENT of plants. For example, it seems you are in USDA Climate Zone
9, which is comparable to San Francisco, California. You would be highly
successful with fuchsia, bulbous begonia, etc. However, here in Hilo,
Hawaii where the lowest temperature year-round rarely hits 60 F, (15.6 C.),
we cannot grow these beauties and there is little horticultural information
on this so we try and fail... however, with some things we do succeed. I am
growing a fine example of the Alaskan Cedar (Chamaecyparis nootkatensis f.
pendula) with no problem at all!

Check this website:


From: "George R Stilwell, Jr." grsjr at juno.com> on 2002.05.21 at 20:50:47(8843)

Zones have only to do with the mean low temperature. There is a new index
to do with heat
being dffered by the USDA. To answer your question, go to


From: "Marge Talt" mtalt at hort.net> on 2002.05.21 at 21:55:50(8845)

The US is so vast with so many different climates that the zone
system was developed using the average low temperature - not exactly
pertinent because our zone 8 covers climates that are extremely
dissimilar...but, it's a start. The American Horticultural Society
has recently developed a heat zone chart along similar lines but for
heat tolerance. It is marginally useful since most plants have not
been rated for it and it does not take into consideration many
climate factors.

From: "Randall M. Story" story at caltech.edu> on 2002.05.22 at 08:03:16(8848)
As people have mentioned, the USDA zone concept is really pretty limited.
For example the foggiest parts of San Francisco, some of the hotter and
drier parts of Southern California as well as Miami Florida are all zone
10!! Yet you certainly can't grow a Coconut Palm in San Francisco (or
anywhere in California that I know of), whereas a Dracula orchid that would
be very happy in coastal California would quickly fry in Florida. And on and

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