The Sacrosanct Hardiness Zones

Now is it 2. 3. 4. 5 or 6?????

I just thought a bunch of you Hardiness Zone aficionados would like to know a little fact about the USDA Hardiness Zone Map. The zone ratings are based upon JUST 12 years of data -- 1974 to 1986. Do you believe 12 years of information make a climate? Well the USDA does. I wonder how they factored in the 50-year weather events or the Storm of the Century. Hmmmmmmmm. But then again statisticians know best. We believe, we believe, we ...

For further information, see

The hardiness zone map is based on the average low temperatures for each zone. If we take the AVERAGE low temperatures for December, January and February it would be in the teens above zero resulting in a Zone 6 or even better.
Or maybe we should take all the record lows for the past 125 years or so and AVERAGE them.
Add December at -18.83?F, January at -25.26?F, and February at -19.38°F for an average of -21.15°F. Now there you have it. This is the AVERAGE of all the observed record low temperatures for December, January and February according to This places us a tad into Zone 4
Or maybe we should just use the coldest day in recorded history. –37?F on January 30, 1951. Not an average at all but the coldest actual air temperature observed in Madison since records were begun. That places us in Zone 3 and almost to Zone 2. So, if you never wish to lose a plant to winter’s cold, only plant things that will survive the once in 150 years of –37?F. All will be wonderful except for the hundreds of other factors that will weaken, eat and infect your plants. Now I wonder what the government statisticians are thinking about rabbits and deer?

A most excellent web site is
This wonderful cold hardiness publication from the University of Maine, Orono, Maine pretty much tells it like it is.

originally published 2001 V15 #2

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