Just like you, Judy, “I like having an idea of whether [a plant] would turn to slime come April before I spend money on it.” I’m always on the lookout for sources of information that keep me from reinventing the wheel. Woody Landscape Plant Cold-Hardiness Ratings, Technical Bulletin #156 from the Maine Agricultural and Forest Experiment Station, is one of the first sources of information I found. UMaine maintains the Lyle E. Littlefield Ornamentals Trial Garden in Orono. According to the Introduction, “the site is in USDA hardiness zone 4a having suffered winter temperatures as low as -30 degrees F. three times in the last 6 years.” (This was published in 1994.) The plants are grown without winter protection except for mulch and are rated numerically to indicate their winter survival: 1= no damage whatsoever and 5=died. However, as Reeser C. Manley pointed out to me in an email dated 3/7/2001, “. . . in some cases only one to a few plants were tested. This is fine if they survive, but tells you nothing if they die since winter survival is a function of so many variables, freezing tolerance being only one.” True enough, but it’s a good place to start if you don’t have a clue as to what trees and shrubs will survive in your climate, and the woody plants are the most expensive. Best of all, the booklet is free for the downloading.
When dealing with frost it is always best to be paranoid. In the spring never think it is too late for one more frost to come. And in the fall never think it too early.
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