Friday, January 18, 2008

January 17, 2008

Global warming has implications for backyard gardeners

by Amy L. Cornell Community columnist |
January 17, 2008

The invitation looked like a thermometer soaring to tropical temperatures. It read, “You are invited to ZONE 6 party!” Was it a welcome to a trendy new Bloomington club? No. Was it a fraternity drinking ritual? No. Would you believe it is an invitation to a party to explore new gardening possibilities — a make-the-best-of-warmer-temps upside to the future with global climate change?

The host, John G, who calls himself an urban homesteader, understands that the conditions under which he gardens are rapidly changing. Crops which formerly would not have been able to withstand the climate in Indiana are now considered at home. Since 1990, our hardiness zone here in south central Indiana has shifted from that of a zone 5 to a zone 6.

A hardiness zone is a geographic location which is capable of supporting certain plant life based on the ability to withstand extremes of low temperature. Any gardener in any zone naturally comes to know what plants will thrive and what plants will die when cultivated outdoors in his/her hardiness zone.

The invitation to this party was this gardener’s recognition of the change in parameters under which he has been growing his garden for the past few years.

I asked him what one brings to a zone 6 party. “Perhaps ideas,” he says. He is looking for new cultivars to try in his backyard garden. He has his eye on this latest nutritional fad — the pomegranate.

All over the country, farmers and gardeners are rethinking what they can and cannot grow in their patch of the sun, given new temperatures and changes in climate.

As I began to look for more information on hardiness zone changes, I found two interesting sources. At, I found an animated map that shows in which hardiness zone Bloomington was way back in 1990 and in which zone it resides now. If you click the image, it shows the trend over 18 years time. It’s a little unsettling to see the bands of orange move higher and higher.

The other source was the USDA and the National Arboretum Web site. The USDA has useful information up about planting and gardening. Their zone map is a 2003 version of the 1990 hardiness map. What is more frightening than bands of orange moving north on the Arbor Day map is that apparently there is no mention or discussion of any of the changes that have been happening to the climate over the past 18 years on the National Arboretum Web site. Does the U.S. government acknowledge the change in growing zones? I know I have noticed the change in temperatures.

When I was a kid in Ohio, snow stayed on the ground from about the first of December to the first of March. I would never have gone to school without a coat in January as my son often does now. My crocuses have been coming up in December.

I’ll admit my perusal of relevant government Web sites was sketchy, but if you know of a source that demonstrates the U.S. government’s acknowledgement that hardiness zones or even temperatures are changing, I would love to see it.

John G wants to grow pomegranates here in Indiana. He might try olives, too. Kiwi, he says, has been done so he is not as interested in that, but he wants to have a zone 6 party so that people realize that growing conditions are substantially different than they were 20 years ago and that possibilities for gardens change all the time. The party will be a little bit global crisis and some gardening imagination with a few seed catalogs thrown in. I may hold out for the zone 10 party — at which time I will finally be able to grow my avocado tree.

Amy Cornell’s column appears every other Thursday in The Herald-Times. You can reach her at

1 comment:

Steph said...

Very interesting, Amy! I'll mention this to my very own gardener b/c he's pretty in tune with the natural cycles. I'll bet he's noticed it, too.