A revised USDA Hardiness Zone map will be released this year, Scientific American reported. Horticulturalists and experts who have helped with the revision expect the new map to extend plants' northern ranges and clearly show the extent of gradual warming over the past few decades. USDA commissioned the revised map after a flap in 2003, when the American Horticultural Society released a draft update based on 16 years of temperature data. USDA had funded the project but rejected the update, which was configured differently and showed significant warming over the 1990 version, with many parts of the nation shifted into warmer climate zones.