Should Climate Change Alter Your Fall Plantings? There’s Room for Debate

Fall is the optimum time to plant many varieties of trees, shrubs, and bulbs. But if you’re looking forward to enjoying the fruits of your labor in the years to come, be aware that hardiness zones may be on the move.

Hardiness zones are areas identified by various organizations as having particular climates. Basically, northern zones are colder and have shorter growing seasons, requiring hardier plants than southern zones.

The gold standard of hardiness zone maps is issued by the U.S. Dept. of Agriculture. But the last update to that map took place in 1990.

In 2006, the National Arbor Day Foundation issued their own map based on research indicating that average temperatures were rising across North America. Their new hardiness zones coincided with a growing public awareness of global warming and received considerable media attention.

Reacting to that data, however, may be premature, says Richard Jauron, a horticulturalist with the Iowa State University Extension service.

“We still use the 1990 USDA map,” says Jauron. “We have yet to see the kind of dramatic climate change that would make it necessary to alter zones and gardening habits.

“In fact, our recent winters are much more in keeping with might be called normal temperatures.”

Although the federal government readily recognizes shifting weather patterns — the EPA has an entire website devoted to climate change — the USDA zone hardiness map remains unaltered.

Meanwhile, what’s a home gardener to do? The best bet is check with your local extension service for advice.

Even better: Seek the recommendations of a local gardener or horticulturalist who’s been in your particular area for many years. Ask if weather patterns are changing, and what plants to put in the ground that will thrive for years to come.

Is the climate changing in your area? Which zone map do you use?