Whether or not you believe global warming is caused by human activities or if you think it's a natural effect of climate change, there is no doubt things are changing.
So much so that for the first time, the U.S. Department of Agriculture has updated the growing regions in its Plant Hardiness Zone Map. This is the guide that gardeners, growers and just about everyone in the plant industry uses to determine which plants will survive the coldest temperatures in various regions of the country.
The map was upgraded in 2003, but rather than a zone change, it was a more detailed map that narrowed down the previous existing zones into sub-categories.
This time, however, the map has changed to reflect changes in climate and it tells the story that here in northeast Ohio, we are getting warmer.
The USDA Plant Hardiness Map basically divides the country into zones based on the average coldest temperatures in winter.
Using the zone map as a guide, growers determine which plants will survive the winter, meaning they are hardy to our area.
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Seed companies use this guide on seed packet labels, growers use it on the tags attached to the plants we buy, and gardeners use this guide to decide when to plant everything from asparagus to zucchini.
According to USDA calculations, each zone is based on 10 degrees Fahrenheit. Prior to the upgrade, which was announced Wednesday, Zone 1 is the coldest at minus 60 to minus 50 degrees, and Zone 11 was the hottest at 60 to 70 degrees in winter, such as Hawaii and Puerto Rico.
Hardiness zones are based on the average annual extreme minimum temperature during a 30-year period, not the lowest temperature that has ever occurred or might occur in the future.
Northeast Ohio was considered Zone 5 until the 2003 upgrade put us in Zone 5A, but temperatures were still based on our area reaching minus 20 to minus 15 degrees in winter. The exception is areas north of us along the shores of the Great Lakes, where water temperatures can create slightly warmer climates.
The updated zone map includes two new zones, 12 and 13. But northeast Ohio, with the exception of a couple minor spots here and there, has been upgraded to Zone 6A. According to the USDA, northeast Ohio's average winter temperatures aren't likely to be colder than minus 5 to minus 10 degrees.
''This opens up a whole new experience,'' said Ohio State University Extension certified Master Gardener Kathleen Ferris.
Ferris, who said she doesn't usually buy plants tagged higher than Zone 5, will now start experimenting with plants that were once considered only hardy to areas south of us.
''We might have to protect them, put them closer to the house or create a wind barrier, but it's certainly worth trying,'' Ferris said.
Ferris, noting that hydrangeas are one of her favorite plants, said there are a lot of hydrangeas that can be grown in Zone 6 that we couldn't grow in Zone 5. With the news of the upgrade, Ferris said she will probably begin buying more Zone 6 plants.
Garden centers and plant retailers may take a more wary approach to the USDA's announcement.
''I see the warming trends, but I also see the change in precipitation,'' said Jim Adgate, owner of Adgate's Garden Center in Cortland. ''With the lack of snow, I think that changes everything. Snow acts as a wonderful insulator and plants that could have been protected by snow may not make it through.''
While the garden center in the past has stocked plants that are considered marginal, Adgate is not so eager to begin telling customers it is safe to plant things that were once considered only hardy to regions further south.
''There's still a big difference between Cincinnati and Cortland,'' he said. ''I can't guarantee a Zone 6 plant to be hardy to our area, and I'm certainly not going to start using them in our landscape designs.''
For information about the upgraded USDA Plant Hardiness Zone Map, visit the website at www.planthardiness.ars.usda.gov/. The website also includes a link where visitors can put in their ZIP code and see how the change has affected their region.
Evanoff is a Master Gardener with The Ohio State University of Trumbull County.