 | In 1997, Dr. H. Marc Cathey, President Emeritus of the American Horticultural Society (AHS), working with the Meteorological Evaluation Service Co. Inc., produced the AHS Plant Heat-Zone Map, thus completing the circle of information available to establish a plant's likelihood for survival from extremes in temperature. The 12-zone map indicates the average number of days each year that a given region experiences "heat days"-those days with temperatures over 86 degrees and the point at which plants experience damage to cellular proteins. The zones range from Zone 1 (with no heat days) to Zone 12 (210 or more heat days).
When used in conjunction with the U.S. Department of Agriculture's Plant Hardiness Zone Map, consumers can now select plants that will thrive in their gardens throughout the year. Since the release of the Heat-Zone Map over 15,000 plants have been coded to indicate heat tolerance.The two ranges, both cold hardiness and heat tolerance, will appear on the Monrovia Infolabel and together give gardeners the ability to better select plants appropriate for their unique climate. | |