Warmer winters changing planting plans

Average winter temperatures have increased across the nation in the past 15 years, and a new analysis by the National Arbor Day Foundation lays out expanded ?hardiness zones? for trees more commonly rooted in Ohio, Illinois, Iowa and points south that could expand their growing range to Minnesota.

?It opens up some new options,? said Woodrow Nelson, the foundation?s communications director. ?People in a much larger portion of Minnesota can experiment with flowering cherry trees, apple trees and even flowering dogwoods.?

The changes proposed may seem less surprising than ever after an unusually warm winter in much of the Midwest, with temperatures running 10 to 20 degrees above normal.

In its study, the Arbor Day Foundation used the last 15 years of data from the National Oceanic and Atmospheric Administration?s 5,000 weather stations to redraw a hardiness zone published by the Department of Agriculture in 1990. The result was a dramatic shift in winter hardiness zones in many states.