By Michael Leach
Baby it’s cold outside — but not as cold as it used to be. At least that’s the impression from the just-released Plant Hardiness Zone Map from the U.S. Dept. of Agriculture. This map shows the lowest temperatures likely during the winter and helps gardeners determine which plants can survive in their area.
For instance, Madison, Wisc. is now considered Zone 5a where the lowest winter temps can fall between -20 to – 15 F. In the last version, produced in 1990, Madison was in Zone 4 (-30 to -20 F). The St. Louis metro area went from Zone 5 (-10 to -20 F) on the 1990 map to Zones 6a (-10 to -5 F) and 6b (-5 to 0) on the new. Cincinnati, however, remains in Zone 6. Gardeners in these areas should select plants rated as hardy in Zone 5 for Madison and Zone 6 for St. Louis and Cincinnati. (Gardeners also should select plants that need the soil, light and water conditions found in their yards but this is gist for another post.)
Maybe the coldest readings in some parts of the Midwest just aren’t as cold as they were when the last map was produced in 1990. But that doesn’t grant us license to succumb to zone envy and begin planting delicate things hardy only in much warmer climes.
No. Caution is advised. There’s one sure bet in the Midwest — extreme weather. Regardless of groundhog prognostications, Easter egg hunts can be snowy affairs in even the warmest parts of the Heartland.