The little maps on the back of garden seed packets are-a-changin." They give plant hardiness information and are important to all of us. Gardeners, arborist, farmers, and botanist---their plant hardiness decisions·affect our food as well as the beauty of plants around us. Plant hardiness zones from the USDA are based on average low temperatures. New zone maps for 2012 have just been released and are based on 1976-2005 data.
In 2011 zone maps were depicted in ten degree Fahrenheit zones. Kentucky was reflected to be predominantly in Zone 7 with average lows 10 to zero Fahrenheit, whereas Northern Kentucky and parts of mountainous regions were Zone 6 with average lows ranging from zero to minus 10 Fahrenheit.
The 2012 zone maps are broken down into 10 degree Fahrenheit zones that are refined into 5 degree segments "a" and "b". Two additional zones have been added so that warmer ranges in Hawaii and Puerto Rico are addressed, bringing the total to 13 zones. The map of Kentucky depicts Zone 7a (zero to 5 Fahrenheit) and Zone 6b (minus 5 to zero Fahrenheit) to be dominating, while Zone 6a (minus 5 to minus 10 Fahrenheit) appears to be a smaller area in this temperature range.
The USDA highlights their web ability to provide data by zip code and refinements which take into account more weather controlling elements such as mountains and bodies of water. This should allow more precision in plant hardiness decisions.
Seth Borenstein of the Associated Press points to zone changes indicative of global warming whereas USDA denies the soundness of using temperature lows as a predictor of change. He points out that "nearly entire states, such as Ohio, Nebraska, and Texas are in warmer zones."
One thing is certain: a massive change will take place in decisions relating to plant hardiness. This change will be imperceptible to most of us. It will range from label changes on fruit tree seedlings, to changes in seed production, in advice to farmers from County Agents, and perhaps to crop loans and insurance. The zone changes will resonate throughout all of agriculture.
For most in the environmental community the evidence of climate change, including warming, is overwhelmingly a scientific fact. Kentuckians can only hope that the palms will be coconut palms.