2012 brings a new and revised Plant Hardiness Zone Map which was recently published by the USDA. This map has 30 years of weather data in it’s making (1976-2005). The previous edition was published in 1990. The hardiness zones are created from the average annual extreme minimum temperatures from the past. Here are a few highlights about the map:
- This is the first PHZM specifically designed for the internet, allowing users to examine zones at a much finer scale. It also has a handy zip code feature. Just type in your zip code and your zone will be reported (I’m in 8b!)
- Two new zones have been added, zone 12 above 50F and zone 13 above 60F. These are for Hawaii and Puerto Rico, but also to assist in keeping tropical ornamental plants that might travel from patio to house.
- This new map is generally a half zone warmer in most areas of the United States as a result of more current weather data, more sophisticated mapping methods and a greater number of station observations.
- Uses the concept that during their lifetimes, perennial plants mostly experience what is termed ‘weather’ rather than ‘climate’. (I’m wondering what I experience during my lifetime? I’m with the perennials I think.)
- Microclimates that are too small to show up on the map should always be considered. These are areas in your yard that might be sheltered or exposed. No map can take the place of local knowledge.