Warming shifts gardeners’ maps
By Elizabeth Weise, USA TODAY
Every gardener is familiar with the multicolor U.S. map of climate zones
on the back of seed packets. It’s the Department of Agriculture’s
indicator of whether a flower, bush or tree will survive the winters in
a given region.
It’s also 18 years old. A growing number of meteorologists and
horticulturists say that because of the warming climate, the 1990 map
doesn’t reflect a trend that home gardeners have noticed for more than a
decade: a gradual shift northward of growing zones for many plants.
The map doesn’t show, for example, that the Southern magnolia, once
limited largely to growing zones ranging from Florida to Virginia, now
can thrive as far north as Pennsylvania. Or that kiwis, long hardy only
as far north as Oklahoma, now might give fruit in St. Louis.