Weathering winter's erratic moods

 Kaarina Dillabough/Flickr

Kaarina Dillabough/Flickr

The pendulum swings of winter have us nervously looking over our shoulders, wondering what tomorrow will bring. One day it’s record-breaking warmth, the next day we’re shivering in single-digit temperatures and hiding from knife-edged winds.

I say that any winter day when the gas meter isn’t twirling around like a merry-go-round or the oil tank isn’t draining with an audible slurp is a good day for the average homeowner. Look at it this way: We’re already one-third of the way through winter and it hasn’t been a terrible ordeal with weekly “snow events.” Some days have been spring-like with temperatures pushing toward 60.

You may wonder about the effects of unseasonable warmth on the garden. Perhaps like me, you've been looking around for signs that the earliest spring bulbs are  breaking ground, poking up their little green noses.

There’s nothing to worry about if you find they’re on the move. Most hardy bulbs are native to harsh climates and can adjust to cycles of warm and cold. Some species, like snowdrops and winter aconite may actually bloom in the snow with no harm done.

The more familiar bulb flowers of spring — daffodils, tulips, hyacinth — are still just a mote in the mother plant’s eye, and won’t emerge until days lengthen and the weather moderates. True, such bulbs may send up leaf shoots and these could potentially be burned by subsequent prolonged freezes. But immature flower buds remain safely ensconced in a wrap of leaves until it’s safe to emerge. Bulbs know what to do.

Among the flowering shrubs and trees, the hardiest fellows like witch hazel, winter jasmine and forsythia are well known for their stalwart natures. Even if it snows after their small flowers bloom, they are likely to shake it off with no harm done.

The trees you may have to worry about — not now, but in fickle April — are large-flowered types like dogwood and magnolia. Once buds swell and fatten with moisture, they can be blasted by late frosts. But for the most part, these old favorites are well-adapted to our climate.

Rhododendrons and azaleas are also May-blooming, and while there may be superficial bud damage from particularly harsh winters, they generally fare well. Rhododendron leaves are a natural thermometer, curling when temperatures drop to the freezing point. The colder it gets, the tighter they curl — it’s an adaptation that limits the surface area exposed to bitterly cold air.

It isn’t cold alone that is the culprit when plants suffer winter damage. Alternating cycles of freeze and thaw are actually more dangerous, since ice in the soil can heave plant roots right out of the earth, leaving them to dry out and die.

 Ice crystals in the soil.                                        kfergos/Flickr

Ice crystals in the soil.                                        kfergos/Flickr

Scientists used to think it was the expansion and contraction of freezing water in the soil that was responsible for shifting plants, cracking paths and roadways and damaging insufficiently anchored pilings and foundations. It’s actually a little more complicated than that.

Frost heave begins when the soil surface freezes, drawing more moisture from unfrozen layers below. Water continues to invade the pores between soil particles until pressure builds up — it can reach 160 pounds per square inch for every degree below freezing, according to an article in Scientific American. That’s pretty hefty, considering that your mechanic’s hydraulic lift needs only about 21 pounds per square inch to raise the average 3,000 pound car.

First aid for frost-heaved plants is no farther away than the heel of your shoe. Press firmly to resettle the plant in the earth, but not so violently as to compact the soil. Your other line of defense is mulch, but many people misunderstand the use of mulch as winter protection. You want to apply a layer of wood chips or whatever after the ground is frozen; the intent is not to keep the little plant roots cozy and warm, but to keep the ground continuously cold, preventing the damaging freeze-thaw cycle.

Snow is actually excellent insulation owing to the air trapping in the fluffy white stuff. Plants are less likely to suffer with a continuous snow cover than if they remain naked and exposed to desiccating winds.

It’s heavy, wet snow and ice that can be damaging, especially to evergreens that catch the load and bend beneath its weight. If you can, go out now before snow falls to loosely wrap conifers with garden twine to prevent branches from breaking. Otherwise, just head outside after any snowfall and gently brush the excess off with a broom.

The other thing gardeners need to be alert to is the potential for critter damage. Hungry deer are on the move, nibbling on trees and shrubs.

Repellents may be effective if applied consistently — try soaking a rag in the worst-smelling stuff you can get and hanging it in the branches. Caging the plants and encouraging your dog to act fierce might also help.

Rodents like to eat the bark from young trees, and can kill them if they remove a ring of bark completely around the trunk — girdling, it’s called. You can buy coiled plastic tree guards that are easy to install around tree trunks; keeping mulch away from the base of the trunk will also deny the little critters a place to do their dirty work under cover.

Chances are good that we and our plants will survive this winter just as we have done in much harsher seasons. Enjoy the relatively balmy temperatures when they capriciously occur. We’ll probably be huddling inside come April if it turns out to be one of those years when winter, having treated us rather kindly, just doesn’t want to go away.