"Rethinking the New Plant Hardiness Zone Map"
"For gardeners sad to see the summer drawing to a close, there's some comfort to be drawn from the fall planting season for perennials, trees and shrubs, which is just around the corner. What's more, there's the novelty of this year's updated Plant Hardiness Zone Map, released early this year."
"The previous version of the map was issued in 2003, but the agency fielded so much criticism over the ways in which it incorporated climate change into the equation -- too little and too much -- that the map was withdrawn, and professional and amateur planters were left with guidelines dating back to 1990.
The 2012 version shows that planting zones have been shifting northward as winters become more mild. But a researcher contends that this long-awaited map is already outdated."Source: Green/NYT, 09/18/2012