With the first day of spring just around the corner, gardeners may be wondering how their plants survived this winter, which was anything but normal – at least what we used to think of as normal up until recently. 

In southern Maine, temperatures were regularly above freezing, sometimes reaching into the 50s. We had no significant snowfall until mid-January, and then it melted fairly quickly. Then in mid-February, with scant snow on the ground to protect the roots of plants, temperatures suddenly dropped to well below zero.

Walking around our own gardens and those of some friends in mid-February, I noticed some daffodils shoots poking up above the ground, buds swelling on our peach tree and, most surprising to me, one lonely Johnny-jump-up violet in blossom in our snow-free vegetable garden. Now, that can’t be normal in February! But by the end of the month, both flower and shoots were covered with snow.

I called some experts to ask what the inconsistent weather may mean for area trees and perennials.

Peaches and sour cherries have suffered some damage, but apples and pears appear to be OK so far, according to Renae Moran, a tree-fruit specialist who works out Highmoor Farm in Monmouth, UMaine’s Agriculture and Forest Experiment Station. During unseasonal winter warm spells, peaches, more than other tree fruits, respond to the warm temperatures by putting out buds. “Those buds start to die around minus 4 degrees Fahrenheit, and at minus 25, all of them are dead,” Moran said.

While the trees themselves are not likely to be damaged, if the flower buds have been killed, the trees won’t produce fruit in the coming season, she said. And if we have another unseasonable warm spell followed by another killing frost, she expects that Highmoor fruit trees could see more damage. “We won’t know until May 15,” she said, the last date that frosts are likely in Monmouth.

Growers can’t do anything to prevent damage to this year’s crop, she said. But for future plantings, they may want to grow fruit tree varieties that produce blossoms later. Another way around unpredictable weather is to plant the trees at higher elevations on the side of hills, because the coldest air usually sinks to lower elevation. Put the stress on “usually.” In rare cases, there are temperature inversions, she said. In any case, while useful to farmers, this solution may not be available to your average home owner who just wants to plant a fruit tree or three in their yard.

Any damage to your perennials by this winter’s oscillating weather will depend a lot on how you prepared your garden for winter last fall, said Pamela Hargest, a University of Maine Extension horticulturist based at Tidewater Farm in Falmouth. “One thing we do in the fall at Tidewater Farm is mulch everything and make sure everything is well-pruned and well-watered before the first frost hits,” she said.

She mulches with wood chips, which the farm has available, as well as plant material. “I’m a big fan of leaving the leaves,” she said. In addition to keeping the plants insulated, they provide habitat for overwintering native wildlife. The mulch serves the same purpose a layer of snow would – if we’d had enough snow this winter – insulating plant roots from sub-zero temperatures.

But most plants that are native to the area should survive these temperature swings (another reason to plant more natives), she said. While rare, such temperature variations have happened over the centuries as these plants have developed. If you’ve planted zone-pushing perennials, bushes and trees in your gardens, plants that really are more comfortable in southern New England than here, you may have problems, though.

In most woody plants, the flower buds are damaged before the leaf buds, according to an article Hargest referred me to by Ron Kujawski of the University of Massachusetts Cooperative Extension. Additional damage comes if the plants do not get to harden off by a gradual decrease in temperatures in the fall, Kujawski wrote, but are hit by a sudden drop to sub-zero temperatures. With herbaceous perennials, it’s the roots that suffer damage.

As with the fruit trees, you can’t do much at this late date to help your plants recover from weather that occurred in December, January and February. Just make sure that this spring, you mulch and water them well. And avoid adding fertilizer until they are growing vigorously. Also, cut out any damaged parts of woody plants, both deciduous and evergreens.

Really cold temperatures do offer one big advantage: It keeps pests from the South away – and I’m not referring to tourists. Last year, after a series of mild winters, the damaging southern pine beetle showed up in Maine for the first time. At the time, State Entomologist Allison Kanoti told me that the beetle can’t survive temperatures below 3.2 degrees. We experienced temperatures well below that at least once this winter. So for now, anyway, any Maine-venturing southern pine beetles may be out of luck.

Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com

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