Why? There may be micro climates that are simply too small to show up on the map. This means, there may be small climate differences in some areas in your yard. For example, you may have small heat islands in beds that are located near concrete or a sheltered area in front of a south-facing wall. Or, you may have an area that's cooler than the rest of your yard, because it's a low spot where cold air pools first. No hardiness zone map can take the place of the detailed knowledge that gardeners pick up about their own gardens through hands-on experience.
But it does give us a great place to start from. So, for most consistent gardening success: Know your Zone.
Blog by: Sabine Ehlers, CMG