Studies show plants that once withered in our cold temps now have a fighting chance thanks to warmer Minnesota winters.
This year, the United States Department of Agriculture has released a new plant hardiness zone map, which breaks up regions into zones according to their average annual extreme minimum temperature. The last map, released in 1990, had Hennepin County in zone 4a, with the average minimum temps reaching 30 below zero. The new map shows a shift, with the county now considered in zone 4b. That indicates average minimum temperatures only dipping to negative 25.
“It just kind of goes to show that, yeah, it has been warming,” says Deb Kvamme, horticulture instructor at Hennepin Tech. “Our winters have been warming since the ‘90s.”
Kvamme says a one to five degree shift is huge for a plant. With the changes, gardeners can now choose perennials they normally would not attempt to plant in this region.
She says items like parsley, magnolias, conifers and some lilies might last longer in the garden. Snow cover can provide insulation, only further helping these types of plants succeed.
Kvamme says, while the map is nice to have, avid gardeners have already been pushing the envelope to test and try new things.
“This is exciting for people that just don’t know their plants very well,” says Kvamme. “It’s a good guide.”
May 8, 2012