[permaculture] New US hardiness zones

SArjuna at aol.com SArjuna at aol.com
Sat Jan 2 19:30:02 EST 2010

You can see the changes in the USA hardiness zones that have been mapped by 
The Arbor Day Foundation at:    


Play will change the map from the 1990 USDA hardiness zones to the 2006 
Arborday.org hardiness zones.    Watch your area carefully as the colors slowly 
 Reset will change the map back to show the 1990 USDA hardiness zones.
 Differences shows colors that represent how much each zone has changed 
since 1990. For example, the pink areas of the map have warmed up enough to 
change one hardiness zone (e.g. the top half of Nebraska has increased by one 

Parts of Wisconsin, where I live, have also changed by one zone.   One area 
in Wisconsin has changed by two zones! (Can someone familiar with that part 
of the state tell me just where that is?) You can also enter your ZIP code 
to find what your new hardiness zone is.]

>From a posting on RealClimate:
> "Most US gardeners are familiar with the USDA hardiness zone map. The
> current (1990) USDA hardiness zone map uses minimum temperatures from
> 1974 to 1986. [ See that map at: www.usna.usda.gov/Hardzone/ushzmap.html] 

The scheduled 2005 update of the map was delayed, and
> rumor has it that the the delay was due to the USDA's unwillingness to
> show how much the US had warmed since the last map. The USDA now plans
> to release an updated map, but this time, using the last 30 years of
> data. As the map reflects temperature minimums, that use of 30 years
> rather than shorter period used for the past two versions will hide the
> warming. 

The US Arbor Day foundation has recalculated the USDA hardiness
> zone map using the 1990 methods and the most recent available data. That
> is, the Arbor Day Foundation map is the modern analog of the 1990 USDA
> map. The resulting graphic of the change in the hardiness zones is
> startling. It's particularly relevant because this map is a tool that
> almost all gardeners use. You'll see it on the back of, well, basically
> any pack of seeds you buy.
> Anyway, I thought this might be a nice way to connect with the average
> American on the issue of climate change. It was also interesting to see
> how much the minimum recorded wintertime temperatures had changed. I
> think I understand that they ought to be more sensitive than the
> average. Even acknowledging that short term changes can be misleading
> indicators of trend, the fact is that the minima did change that much.
> Whether or not the new map will be a reliable guide for the next 15
> years is unknown. But that there were very large changes in wintertime
> minima is a fact, nicely illustrated on the link above."

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