USDA announces new plant hardiness zones

BURLINGTON, Conn. (WFSB) – USDA plant hardiness zones categorize areas based on their average minimum winter temperatures.

But with our warming climate many parts of our state have moved to higher zones, indicating milder winters and longer growing seasons.

While this sounds generally beneficial there are some important things to note before planting.

Connecticut is on average five degrees warmer than a decade ago, which means gardeners would expect more southern plant species to survive our winters.

But growers Channel 3 spoke to say this is a bit of wishful thinking.

“They have changed the map. I personally don’t agree with it. I don’t think that it is appropriate because if we get one of those really cold winters, that’s going to bring us right back to the zone that we used to be,” said Kaitlyn Larson Parker, Owner, Larson Garden Center.

Our state no longer has Zone 5B, which was in the northwest corner of the state and accounted for the coldest temperatures of -15 to -10°f.

Most of Connecticut is now in Zone 6 with a large area along the shoreline in Zone 7. Zone 7 extends all the way south to parts of Virginia.

“A 7 is still a little scary for me to say, but I would definitely say that they are in a generally warmer climate than us anyway, so that’s why things like hydrangea bloom better because their bud hardiness level is so sensitive. So having it closer to the shore where we know it’s a little bit warmer, they thrive there. Up here where we are, not so much,” said Parker.

While the winter minimum temperatures might be warming, that doesn’t mean we won’t get winter cold snaps that will plunge the temperatures well below those minimums.

USDA zones are based on averages, not isolated events, and plants can be killed if the temperatures in the winter dip too low regardless of what the new map says.

“The other thing on top of it is our decrease in snowfall. So our snowfall usually creates a blanket, having this lush kind of snow covering is an insulating factor,” Parker explained.

While we won’t be seeing hibiscus flowers blooming out of snow banks, some examples of plants that can typically be grown in Zone 7 but may struggle in Zone 6 are pomegranate and fig trees as well as certain varieties of gardenia and hydrangeas.

“Each one of us is a little bit different. We have our little pockets here and there. And to be able to say that all of it’s safe, now we can bring in things like tropical hibiscus and plant it and hope it’s going to come back every year, is not really realistic unless you’re a gambler,” Parker said.

The experts say if you’re testing marginally hardy plants based on the new map, plant them in microclimate areas such as near your house, or garage, or in the shelter of other trees and shrubs where they are protected from any extreme cold snaps.