Warming shifts gardeners’ maps

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.

Such shifts have put the USDA’s map at the center of a new chapter in the debate over how government should respond to climate changes that were described in a report last year by a United Nations-backed panel of scientists. The panel said there was “unequivocal” evidence of global warming fueled by carbon dioxide emissions, which have created an excess of the greenhouse gases that warm the Earth.

USA Today