Thursday, May 3, 2012
In January the USDA released their first official update of the Hardiness Zone Maps in two decades. The changes are more subtle than one might have expected based on our memories of experience! The shift marks an approximate 5 degree warming (Fahrenheit) which translates in half zone jumps. There are some cooler areas as well.
The zone maps do not reflect the coldest or the warmest temperatures experienced, but the average minimum temperature at a given location over 30 years. Each zone represents a ten-degree range.
The current map is based on thirty years of weather data (1976-2005). The hardiness zones also represent weather (short term) rather than climate (long term, ie, 50-100+ years).
Although the data does show a warming trend across the New England we experience our individual properties within a local micro-climate, which may or may not mirror this map. Your property may fall one or two zones higher if you are a south-facing and sheltered, or lower if in the north shadow of a mountain!
http://planthardiness.ars.usda.gov/PHZMWeb/ will take you to the new map which is interactive. Click or enter your state. Enter your zip code to simply get a zone readout.