Re: [gardeners] New hardiness zones -- get the fan

Dan Dixon (
Thu, 29 May 2003 10:47:41 -0500

Terry at wrote:

> Egad!  They've moved me to zone 6!  They used to have me in zone 5 and I've
> always had to move down to zone 4 when buying plants to get them to survive.
> Granted, we haven't had a zone 4 winter for several years and this past
> winter our low was the lowest it has been since this drought started, only
> down to -11.  I wonder if they have based this map only on the past 4 or 5
> year's weather?

A detailed description of this map can be read here:

Among other things, it says that this map is a draft which is still under
review by the USDA (hence, the blurb at the bottom of the legend that says
the map does not necessarily reflect the USDA's view).

It also says "Unlike previous maps, the 2003 map was created digitally. 'It
has a higher level of resolution and shows smaller areas of change called
microclimates,' says AHS President Emeritus Dr. H. Marc Cathey, who
coordinated development of the updated map. 'These microclimates include
warmer areas around major cities, which tend to hold more heat because they
have a high density of buildings and large areas of concrete and blacktop.
You can also see cooler areas that may indicate higher elevations.'"

It's also worth noting that the hardiness map is not a "heat zone" map.

BTW, the USDA's "boss" never denied that global warming was occurring,
though he obviously questioned the premise that the Kyoto protocol would
have had any effect on it. Good call, given that countries where air
pollution is rising the fastest (e/g Mexico, India & China) would have
effectively been exempt, while developed countries where pollution is
declining the fastest would be penalized the most.

Dan Dixon