|planting early lettuce|
The zones define a minimum range of temperatures that a plant or tree can survive safely in that zone.
The most common are the Hardiness Zones defined by the U.S. Department of Agriculture (USDA).
In 2012 the USDA released an updated New Jersey hardiness zone map covering the period of 1981-2010. Believe what you will about climate change, but the trees are blooming earlier the past few decades.
|warm weather planting - tomatoes|
In 2012, trees started blooming around March 5. In 2010, after a warm spell at the end of March, the trees bloomed by April 1st.
For my part of NJ, we are in Zone 6B. The average first frost is between October 11 - 20 and the average last frost is April 11 - 20.