Subject: [NAFEX] Accurate well defined hardiness map.
Date: Wed, 21 Dec 2005 21:53:12 EST
There is no such thing.
If you found one that divides down to the county level it will be meaningless. Each zone has a 10 degree difference, and just because a line might be drawn on a county line, those counties will not have average temps 10 degrees warmer or colder than the other. Also those temp ranges aren't absolute. My zone 5b (-15 to -5, my extrapolation) regularly sees -20 and the record is -32.
Conclusion: A well defined map is meaningless. Close counts in horse shoes (the game), hand grenades and USDA Hardiness Zones.
Opinion time: Add at least one zone to what most nursery catalogs list their material to be hardy too. If they say zone 5, if might survive zone 6 over a long time period.
Stephen is correct when he writes: Even in a very large area of a single zone, one might live in a microclimate; I might add, those microclimates can be much colder as well as warmer.
Jerry
[NAFEX] Accurate well defined hardiness map.,
Jwlehman, 12/21/2005