Plant Hardiness Zones

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I’m Charlie Nardozzi and this is the Vermont Garden Journal. I’m back for another year of the Vermont Garden Journal. With the mild, mostly snowless winter and warm spring so far, it feels like it’s planting time already.  All this erratic weather makes me wonder about the effects of global warming on plant hardiness. Plant hardiness zones is a USDA system of mapping out average winter minimum temperatures across the country so gardeners can know what perennial flowers, trees, and shrubs most likely will survive in their area.

This map was last updated in 1990 and now there’s a new version based on 30 years of weather data. What has changed is not surprising to most of us. The map has generally shifted one-half of a zone warmer throughout the country. This means many zone 4 areas in Vermont are now zone 5 and the area in the North East Kingdom considered zone 3, has gotten smaller. Zone 5 now stretches from Massachusetts up the Champlain Valley to St. Albans. There also is a large zone 5 area running up the Connecticut River Valley to White River Junction. What does this mean for a home gardener? Well, for my zone 5 garden it may mean the difference between butterfly bushes surviving, peaches and sweet cherries producing consistent crops, and Japanese maples growing into large trees.

But before you go out and start buying all new plants, be aware that the hardiness zone is an average winter minimum temperature. With our widely fluctuating winters, we could still have winter nights dipping in the minus 20 and 30 ranges which would spell doom for zone 5 plants. So, be careful and locate marginal plants in protected spots.

Now for this week’s tip, order your bare root fruit trees and berry bushes now. Bare root trees and berries are smaller than container ones in the nursery, but less expensive and you’ll have a larger selection of varieties to choose from.

Next week on the Vermont Garden Journal, I’ll be talking about Italian Vegetables. For now, I’ll be seeing you in the garden!


USDA 2012 Plant Hardiness Zone Map

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