Daffodils in January

Daffodils in my woodland garden yesterday. They’ve been in bloom for a week now. Surely this should not be. Which brings me to a new version of the US Plant Hardiness Zone Map released this week.

The U.S. Department of Agriculture has advised gardeners and farmers to count on warmer weather. The map’s colour-coded zones are widely used as a guide for what perennial flowers will survive in a particular area, or when to plant crops. What's being measured is the average low temperature during wintertime. Higher zone numbers indicate a warmer average.

On this map, the zones have all shifted northward, showing that in much of the country, winters aren't as cold as they used to be, and spring planting comes earlier. 

When the Department of Agriculture introduced their new map to reporters, the nationwide shift in the planting season provoked lots of questions about just how much to attribute to climate change. But NPR reports that officials insisted they were making no claims about global warming. Quite right too. They need to eat. There's an election coming. And who knows, the next President may not like global warming.

The new map includes 13 zones, with the addition for the first time of zones 12 (50-60 degrees F) and 13 (60-70 degrees F). It replaces one issued in 1990.