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Impact of extreme weather on landscape, trees

May 19, 2010
Adirondack Daily Enterprise

This spring's unseasonably warm weather (temperatures peaked out at near 90 degrees F in some locations in April) encouraged many trees and shrubs to leaf out one, two, even three weeks earlier than normal. Unfortunately, that left an awful lot of calendar time for things to change. Dramatically!

Leave it to our unfailingly erratic weather to even the score with a series of winter storms and at or near-record breaking cold temperatures in early May. During that time I received a number of inquiries from gardeners and homeowners concerned about the effects that snow accumulations and several mornings of sub-freezing temperatures might have on their landscape perennials, shrubs and trees; especially fruit trees that were budding or fully blossomed out, and what actions they might take to help their trees recover.

Hard frost in early May is not at all uncommon in northern New York. As to the possible effects the freeze may have had on lawn and landscape trees and shrubs; while it's true that newly emerged growth is often tender and highly susceptible to damage from below freezing temperatures, healthy, vigorous, well-established trees should be fine. They should have more than enough stored energy to readily replace the browned or blackened, shriveled, and/or flaccid leaves that have dropped off or will eventually drop off with new ones. And, they can do so in just a matter of weeks, with very little overall impact to their health.

On the other hand, trees that were already stressed or in decline could decline further. And affected trees or shrubs that have not put on new leaves by mid-June most likely never will.

The best answer that I can offer is to just wait it out and let the trees recover on their own. I am endlessly amazed by the ability of trees and plants to withstand adversity.

For freeze-damaged perennials, the overall probability is that only the foliage was damaged. In all likelihood, the crowns and roots were unharmed, and the plants have started tosend up new growth already.

As is the case with all trees, there is usually a slow progression of development as apple trees come out of the dormancy of winter. Dormant buds show absolutely no growth, but as the tree breaks dormancy, the buds begin to swell, until green leaf tissue emerges from the end of the once-dormant buds. As they develop, the buds become more and more susceptible to cold temperatures and frost or freeze damage.

With apple buds, small spur leaves eventually fold back and a flower cluster within the bud is revealed. It continues to grow, and soon individual flower buds within the cluster are exposed. They soon separate and the flowers begin to open. Finally, the flower petals fall and the fruit begins to develop.

Many of the growers I've talked with say that this spring brought the earliest bud break that they can remember. In a recent interview with Martha Foley on North Country Public Radio, Cooperative Extension Northeast New York Commercial Fruit Program Area Specialist Kevin Iungerman stated that "the early start to the season increased risk" because it "extended the window of frost opportunity dramatically."

During that interview, Iungerman explained that at 28 degrees F, "you might expect 10 percent kill" and at temperatures of 25 degrees F, "you might expect up to 90 percent mortality." He also maintained that trees with young fruitlets will experience "injury comparable to what we might find at full bloom or even at first bloom," and went on to explain that "singed blossoms" are not necessarily reason to panic because "different portions of the tissue of a bud and also the fruitlet will freeze at different temperatures."

"You'll have a range of temperature from the ground through the tree," he said, "and at different locations in terms of where the orchards are."

In his role as Extension Orchard Specialist, Iungerman has responsibilities in Albany, Saratoga, Washington, Essex and Clinton counties. While monitoring the situation in Peru, at perhaps the coldest location that he visited, he took a sampling of 100 buds in several stages of development. He pointed out, "Of the hundred flowers that I sliced through to examine, I saw 66 buds (young fruitlets) that I would guess were dead and 44 that were alive." He went on to say that that sampling was from a "very extreme cold pocket" calling it a "worst case scenario," and that he was "encouraged" by that fact because, "basically, going into warmer areas" you will have "significantly more fruitlets that are in better condition and an apple tree only needs a relatively small percentage of its overall fruitlet capacity to have a good crop, or to even have a fair crop." Iungerman will be re-evaluating the situation once the fruit in the region has grown to 12 to 13 millimeters in size.



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