"USNA – USDA Plant Hardiness Zone Map:North-Midwest US" MN "USNA – USDA Plant Hardiness Zone Map: North-Midwest US" "USNA â USDA Plant Hardiness Zone Map:North-Midwest US" ND WI "USNA – USDA Plant Hardiness Zone Map:North-Midwest US" hardiness map for Minnesota MT "USNA – USDA Plant Hardiness Zone Map:North-Midwest US" "USNA - USDA Plant Hardiness Zone Map:North-Midwest US" USDA plant hardiness zone map SD NE "USNA – USDA Plant Hardiness Zone Map:North-Midwest US" WY Minnesota's average minimum winter temperatures http://www.usna.usda.gov/Hardzone/hzm-nm1.html IA Zone 4