Plant Hardiness Zone Maps

Not by Fire but by Ice



Plant Hardiness Zone Maps

It's getting colder . . . and the plants know it

In 1960, the United States Department of Agriculture (USDA) published a Plant Hardiness Zone Map. That’s the map you see on the back of seed packets. Farmers and gardeners use the map to learn where it’s safest to plant various kinds of crops.

The Plant Hardiness Zone Map divides the US and Canada into zones. Each zone represents a 10 degree F (5.6 degree C) difference in average annual minimum temperature. Most of Canada lies in zone 1 (below -50F), whereas most of Florida lies in zone 9 (between 20 to 30F). The higher the number, in other words, the warmer.
Thirty years later, the USDA compiled a new map. Compare the two maps, and you’ll see that plant hardiness zones in many states have moved south dramatically (meaning that it’s getting colder).
Take Indiana. In 1960, more than half of Indiana was in plant hardiness zone 6. Today, most of the state lies in plant hardiness zone 5.

Or look at Tennessee. In 1960, all of Tennessee - all of it - was in plant hardiness zone 7. And today? Three quarters of the state lies in plant hardiness zone 6.

Similar declines have occurred in Illinois, North Carolina, South Carolina, Missouri, Kentucky, and many other states.

It’s getting colder . . . and the plants know it.

So does the United States government, at least one branch of it.

Farmers and gardeners need to know it, too, so they can adjust their crops accordingly.

Everyone needs to know it.


Order Book l E-Mail Robert l Q & A l Book Reviews l Press Release l Radio Interviews l Excerpts l Plant Hardiness Zone Maps l Author Photo l Extent of Previous Glaciation l Crane Buried in Antarctic Ice Sheet l Ice Ages and Magnetic Reversals l Table of Contents l It's Ocean Warming l Expanding Glaciers