Zones of Plant Hardiness
    Zone 1: below -50°F
    Zone 2: -50°F to -40°F
    Zone 3: -40°F to -30°F
    Zone 4: -30°F to -20°F
    Zone 5: -20°F to -10°F
    Zone 6: -10°F to 0°F
    Zone 7: 0°F to 10°F
    Zone 8: 10°F to 20°F
    Zone 9: 20°F to 30°F
    Zone 10: 30°F to 40°F

    Zone boundary lines are not absolute. You can expect temperatures to vary as much as five degrees from those given in the top column. You must also consider localized conditions. Hills and valleys in certain areas do not always have high and low temperatures corresponding to those recorded at the offical weather bureau stations.

    Still other conditions to consider before selecting roses are rainfall, humidity, snow coverage, wind and soil type. A shrub may survive in zone 3 in Maine, for example, but be completely unadapted in the same zone in North Dakota simply becouse of differences in rainfall and humitity.

    Last advice: Keep your rose bushes healthy. Healthy ones will survive the severest winters while week ones probably won't.