The recently released USDA Plant Zone Hardiness Map, updating the previous 26-year-old zone map, reflects rising mean temperatures throughout the country, including Maine, where gardeners must carefully consider possible temperature dips as they anticipate spring planting. University of Maine Cooperative Extension professor and ornamental horticulture specialist Lois Berg Stack is available to explain what the read more Horticulturist Explains New USDA Plant Hardiness Map