A Note on Hardiness Zones
Zone maps outline the different zones in which various types of trees, shrubs and herbaceous plants will most likely survive. It is based on the average climatic conditions of each area. It is an excellent starting point if you are wondering if a certain plant will over-winter successfully. Use the maps for reference, but please check with other gardeners in your area.
The new Canadian hardiness map is divided into nine major zones: the harshest is 0 and the mildest is 8. Relatively few plants are suited to zone 0. The U.S. Zone map (contiguous states) has zones 3-10. Local 'micro-zones' are too small to be captured on these maps. Year-to-year variations in weather and gardening techniques can also have a significant impact on plant survival in any particular location. For detailed information on your hardiness zone see Growing Zones.