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Great Gardening: It’s too early to assess impact of cold snap

It’s April and it’s winter. My thermometer showed 7 degrees one morning at my house. How damaging will this cold spell be for our crops? What will this do to our daffodils, hydrangeas, lilacs and fruit trees? Those were the questions that I and every other landscape and nursery pro heard throughout Plantasia, and I expect we’ll hear all week. This particular pattern is not all that unusual – nearly always some freezes and snow into May – but psychologically it’s tough to face. The daffodils look so very sad, bent under the crusty snow. After a mild winter and warm, teasing days, we were so ready for spring gardening.

A nurseryman’s view

Rob Turnbull (Turnbull’s Nursery, North Collins) grows bare-root trees and shrubs and offers a wide selection of fruit trees, berries and potted plants. Overall, Turnbull the optimist said, “It’s not horrible, this cold spell. It helped that about two and a half weeks ago we had some 15 degree nights, which kept things dormant a little longer. We even dropped plastic (uncovered some hoop houses) to let in the cold so plants wouldn’t break dormancy. But the timing is always a guessing game.”

That’s the factor that many consumers don’t understand when they arrive at their favorite garden centers expecting to see flowering plants. The longer the plants stay dormant, the less likely they are to be damaged. Sellers or customers who rush the season are more likely to lose their bets. And timing is so important. As Turnbull said, “If this (cold snap) happened in 10 more days, we could have lost a lot.”

Nipped in the bud

If drastic freezes happen when woody plants are dormant, the plants will be fine. If the plants have started to sprout or unfurl leaves, that too will be fine: A few leaves may be browned or distorted, but the plant will produce many more leaves. But flower buds are much more vulnerable. They are easily damaged by ice and extreme cold. If the buds were already well formed and fleshy – some lilacs, some hydrangeas – then a freezing night can “nip them in the bud.” This is why I always urge you not to uncover any shrubs, such as the ‘Endless Summer’ kinds of hydrangeas (H. macrophylla, the repeat blooming ones), that you have protected with a Shrub Coat or Shrub Cover (or burlap). Wait until the danger of these late freezes has passed. Lilacs are tough plants and won’t be killed but sometimes the buds are nipped and flowers are fewer.

In the world of trees, it’s also good to keep the big picture in mind. ISA certified arborist Tom Draves (Draves Tree Service and Arboretum) reminds us: “Trees have been evolving for millions of years and we don’t need to respond to ‘gloom and doom’ weather reports.” Proper tree maintenance, and placing trees that are appropriate for the site and the region are important, of course.

Turnbull expects no large crop losses, but says some plants may be less “saleable.” He said some ‘Ivory Silk’ tree lilacs for instance “pushed out too far” so they will be “burnt back.” Most consumers fall in love with plants when they are flowering, so a tree lilac without the cloudlike flower puffs probably won’t sell this year, no matter how healthy it is. Turnbull said they did manage to rewrap the ‘Endless Summers’ and “tuck them back into bed.”

What could be more serious, and I believe it’s too soon to tell: Fruit trees and grapevines in some parts of Erie and Niagara counties could have fattened up their flower buds (without which there is no fruit) a bit too soon. The National Weather Service tells us that damage occurs to fruit tree flower buds at different temperatures: “The more advanced apple trees will start damage at 23 degrees, damage to peaches at 23 degrees, and cherries at 24 degrees. Temperatures of 18 or 19 degrees will cause more substantial injury.” So, depending on several factors, some fruit buds could be nipped. Let’s hope not.

More than plants affected

An e-list mailing came to me from Masterson’s Garden Center and Aquatic Nursery (East Aurora) which specializes in honey bee products and beekeeper training, reminding me that it’s not just about the plants. Mike and son Dan wrote, “With teens and even single digit temps in the forecast… Please make sure your hives have plenty of honey stores or enough food patties to make it through. Queens have already started laying eggs in most hives, so the bees will be burning up more fuel to keep the expanded brood nest warm.” They, and many other living things have some compensating to do when Mother Nature throws us curve balls in spring.

Farmers and growers gamble

Besides the birds and the bees, the pros that grow our food and flowers take a hit when weather extremes occur. When cold spells like this one happen, farmers and growers have to adjust work schedules, which affects staffing now and alters when the first crops can be harvested later. This weather makes farmers stop tilling and slows down planting, and it’s a guessing game how soon to plant. Wet soil governs many decisions too; not every field has perfect drainage.

Nurserymen have similar gambles: when to remove plastic, when to move woody plants outside (from an unheated greenhouse or hoop house), when to move herbaceous plants from a heated house to an unheated one. Your nursery staff, from north to south, are making decisions and moving plants based on weather predictions, history and available labor, space and time. Not simple.

In the world of bare-root plants, it’s a little different: Rob Turnbull said they sold lots of plants in the warm spell in March and the nursery generally holds the purchases in cold storage to keep them dormant until planting time. He called this return to winter a good reality check: “People were rushing the season. The worst effect I see is more depressed people!”

Sally Cunningham is a garden writer, lecturer and consultant.