This might become a regular topic on my blog. So many times I find myself down deep in rabbit holes when researching. You’ve never done that, I’m sure. As I’m preparing for the “Not Just Farmers” course for GRIP, I am finding myself on many a winding research paths and then I wonder how I got there!

This week’s rabbit hole brought to you by “History of Plant Hardiness Zone Maps” found on the Plant Delights Nursery, Inc. website. You know, those maps you find on the backs of seed packets or in gardening books. Like this one from the U.S. Department of Agriculture.

The history of these maps is fascinating. I won’t restate everything. You can click on the link to the article above and read for yourself. But what I found most interesting is that the first such map was published by the Arnold Arboretum at Harvard University in 1927 and compiled by Dr. Alfred Rehder from data collected from a survey about plants and their survivability in different regions. In 1938, the Arboretum published another map based on 40 years of data from the U. S. Weather Bureau.

It wasn’t until 1960 that the USDA published its first map…based on different data…resulting in conflicting information. The Arnold Arboretum maps remained the standard until 1990, “when the US Department of Agriculture, in cooperation with the U.S. National Arboretum, updated the USDA hardiness map, using data from between 4,800 to 14,500 weather stations.”

Following rabbit holes can really dig up a lot of information that may or may not be included in the course, or that course could last 2 full weeks or more! But this information can be useful in understanding our farming ancestors a little more deeply, perhaps. And may be useful come pub trivia night!