Living on Earth (NPR radio show) asked the question of why it’s been 18 since the last one.
GELLERMAN: So why hasn’t the United States Department of Agriculture released a new hardiness zone map in almost 20 years? I put the question to the USDA’s Kim Kaplan.
KAPLAN: Well there’s actually been no set interval between any two editions of the USDA Plant Hardiness Zone Map. One of the things that drove this one, frankly, is that the government printing office called and told us they were out of the old one, and should they print the same one again or were we going to do a new one. Because the old one was done in 1990 and predates the internet, it was not digital, and we knew we wanted to go to something that was state-of-the-art – something GPS, GIS compatible, much more detailed and much more sophisticated and most importantly web-friendly.
It’s expected in months not years.