Upside Down Under: Hardiness zone changes. . .

Back in the 1960s, the United States Department of Agriculture produced a map of the nation with a number of hardiness zones to help guide gardeners and landscapers with better planting advice.

However, those early maps don’t reflect the same zones as today’s maps. There are no doubt, warmer, albeit slightly, patterns that are moving farther north. In fact, when you take North Dakota into account,...