Subject: Re: ?? USDA Hardiness Zones for the World
From: wtmorgan@pilot.msu.edu (Bill Morgan)
Organization: Michigan State University
Date: Thu, 06 Nov 1997 12:35:07 -0500
Message-ID: <MOD$971106.23429@rec.gardens.ecosystems>
References: <MOD$971105.6326@rec.gardens.ecosystems>


In article <MOD$971105.6326@rec.gardens.ecosystems>, metazoan@mediaone.net
wrote:

> Hello,
>
> I am developing a large nature community on the internet and am in need
> of some USDA Hardiness Zone Charts for for the rest of the world....I
> have found some beautiful zone maps for the North American continent but
> can not find any that correspond for South America, Africa, Austalia,
> etc (I found one for Europe but it wasn't very detailed). If anyone
> knows of any place on the net or otherwise I could get these, I'd
> appreciate it. I have the temperature charts but I'd also like it in
> graphical form for the website.
>

Cindy:

Since the USDA is concerned with the US, you probably won't find USDA maps
as such for the rest of the world. There actually *is* a USDA map for
Canada using the same scheme as the US map, and there is a Euromap with
similar zones (but with zones offset from the US equivalents by about 5
degrees F). You can find all of these in "Gardening for Dummies" by Michael
MacCaskey. (IDG Books Worldwide, ISBN 1-56884-644-4). The same book has a
table which gives minimum temperatures and USDA zone equivalents in many
major cities around the globe.

These maps have a limited utility, IMO. They do one thing reasonably well:
they give you an idea as to how cold it gets in any given area, so you can
select plants accordingly. In fairness, that's all they were designed to
do, and this information is valuable in its own right.

Unfortunately, many people regard these zones as being "climatic zones",
which is not the case. Just because you can get a plant through winter
cold, for example, doesn't mean it will survive the summer's heat (or
dryness). Or a zone which has a mild winter may also have a cool cloudy
summer, which does not bode well for heat and sun loving plants.

The best example I know of the latter phenomenon comes from the animal
world. No turtles are native to Britain, and attempts to introduce them
have failed. Why? because it is too cold. But wait! There are turtles
throughout Michigan, some areas of which get far colder in the winter than
it does in most of the UK. What's the deal? The *summers* are too cold--not
enough warmth for eggs to hatch.

The Sunset zone system is more comprehensive than the USDA system, as it
includes more different factors: heat, rainfall, length of growing season,
etc. This makes their zones more nearly true climatic zones.
Unfortunately, this is a proprietary system, so you can't just put it on
any old website. Also, this system is not without it's critics, either.
Some people object, for example to the size of zone 1: it is enormous,
stretching from the Dakotas to Arizona and from Arizona to Washington
(IIRC). Of course, the information here is still useful even with its
faults. And if anyone has a better system, I'd like to see it.

But whatever regional information one may have, it is just a starting
point, IMO. Your immediate microclimate may run several degrees hotter or
colder than that of an area only a few hundred yards away, effectively
moving you by half a zone one way or the other. Certain cultural practices
(esp. tricks of perennial care over the winter) can make a great difference
in what will work in your area. And of course, the big uncertainty:
climates are not static, they change all the time.

But good luck with your endeavor.

Regards,
Bill

--
Bill Morgan
wtmorgan@pilot.msu.edu
Center for Room Temperature Confusion