Coping with spring frost

MD-gardening column 2x-04116
It’s not that we didn’t know freezing temperatures might strike our gardens in Spring, it’s that it happened after more than a few days of baking hot weather in March and early April, with thermometers registering in the barely believable high 70s and even 80 degrees.

One day people were mowing their lawns in T-shirts and birds were falling in love and singing arias by the bathroom window. The next day one was rummaging for long-johns in the dirty clothes hamper.

Last Saturday, bitter winds, frost and a brief snowfall dispelled all fantasies of summer. In its wake, the weather left shriveled buds, burned by the cold.

My peach tree had bloomed and held open house for many pollinators long before last weekend, thank goodness. But stopping in to buy bird seed at Bennett’s (formerly Wayne’s) in Cambridge, I heard of a peach orchard where trees were sprayed with water to protect the flowers from impending frost. The attempt failed.

Two hydrangea bushes in my garden had each produced a beautiful set of perfect, tender green leaves, causing the gardener to compliment them daily on their achievement. But a frost early last week reduced a third of them to shriveled black curls.

On Sunday, I looked out the window, expecting to see total disaster after Saturday night’s gales. Wind multiplies the effect of frost. Miraculously, the leaves that had survived the frost several days earlier remained intact.
Many people wait until after the last spring frost to put in a vegetable garden. I’ve heard people say they do it “after Mother’s Day,” which is almost four weeks away, on May 8. But some gardeners, tempted by the summer-like weather we experienced, planted early this year.

A friend of mine planted his potatoes well before St. Patrick’s Day, the first date recommended by the University of Maryland Extension Service to put in potatoes and peas. When I asked him how they’d fared, he said “Fine!” He’d covered up his backyard crop with sheets of plastic after hearing forecasts of frost. Planning is everything, in gardening as in life.
Plants vary greatly as to how they tolerate cold. Raspberries, for instance, grow really well up north and sometimes have a hard time in the sticky hot summers here in Dorchester. Mine appear to have sailed through the recent spell of frost unscathed.
One of the things a gardener can do to plan ahead for untimely bitter weather is to choose plants bred for improved cold hardiness. Dwarf and semi-dwarf fruit trees, for example, resist cold better than do full-sized fruit trees. Of course, they’re more expensive, but they offer other advantages, too. They’re easier to prune, spray and harvest and they start to produce fruit sooner than normal sized trees.

Another factor is location. Where you put your plants can make a huge difference in how they hold up to nasty cold spells. My hydrangeas live by the side of the house exposed to sometimes violent winds and shaded in the morning by the house’s shadow. I planted them long before I became a master gardener. The idea was to protect them from the worst heat of summer, when they wilt and need watering daily.

Fruit trees should be planted in full sun so they get plenty of light to make the energy they will need to grow, produce fruit and withstand trying weather. Sitting in the sun – whether them or us – maximizes the chance of catching some warmth, even on the coldest days. If you doubt it, try having breakfast in a sunny spot, compared with a room where no sun penetrates. The sun will warm you right up, believe me, I did it this morning.

When choosing planting sites, scout out so-called frost pockets — areas of your yard where cold air collects – so you can avoid them. To find them, look for the last areas that remain dusted with silvery grey frost after all the other frost has melted.

It sounds counter-intuitive, but the Maryland University Master Gardener Handbook says planting fruit trees on a gentle slope facing north is ideal because cold air moves down a hill, helping to reduce frost damage to trees planted at the top and about three-quarters of the way down the slope. (Don’t plant further down, or you may encounter a frost pocket.) And because northern exposures are always cooler, trees there will delay flowering, reducing the chance of buds opening at a time when they might get burned by a late-spring frost.

(This being the Eastern Shore and flat as a pancake, you may be thinking: “Slope? What slope? “All I can say is that I’ve seen a few slopes here and there in the County. If you don’t have one and you want one, consider having enough good soil trucked in to make a slope. Admittedly, it’s not cheap.)
Conversely, picking a southern exposure – which you’d imagine, and so would I, to be perfect – is actually a stupid idea because the extra warmth from facing Florida, etc., will encourage fruit trees to flower early, then along will come a frost and there go your chances of having home-grown fruit that year.

Stone fruits are particularly susceptible to frost. Don’t plant cherry trees and apricot trees here unless you’re prepared to get no fruit fairly often. If you want fancy fruit, move to Florida (or wherever cherries and apricots grow). Personally, I couldn’t be happier than with the peaches and strawberries grown here.

As for vegetables, if you want to extend the planting season by starting before the threat of spring frost is over, plant hardy and semi-hardy crops like kale, collards, arugula, multiplier onions, parsley and spinach. Protect them with cold frames, floating row covers or tunnels made from clear plastic sheeting stretched over a plastic or wooden frame.

A tunnel can be as simple as clear plastic stretched over hoops that straddle the plants. Make sure to anchor the edges with something heavy, like bricks, to keep the warmth in and pests out.

If it’s sunny and warm as you read this, remember we’re not out of the woods yet. Dorchester could get its final frost as late as the end of April, or beyond. So be prepared. In the meantime, happy gardening!

Editor’s Note: Laetitia Sands is a master gardener in Dorchester County.

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