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Has the record warmth already done harm to plants?

Last week the shorts and tees came out of the dressers. Joggers jogged and dogs ran in the parks. Some people as well as plants became confused. Is it spring already?

While the record-warm days of mid-February felt great for most people, it was not a good thing from a horticulture perspective. Wine grape producer Rick Walker commented: "The winter weather certainly has been comfortable for us — but that is the only blessing."

Steady, cold weather is like a seat belt for the crops, he explained. The plants are safe when the ground is frozen. A warm spell in winter is like taking off that seat belt: Suddenly the plants and their fruit buds are put in danger. Walker is the owner of Walker’s Fruit Farms in Forestville, one of the largest wine juice producers in the country, and he knows all too much about the effect of all weather extremes, from the historic drought of the summer of 2016 to unusual winter weather patterns.

The question then arises: Don’t we always have temperature fluctuations in winter? Isn’t a January thaw typical in our region? The answer is yes, but not all temperature ups and downs are the same. Some changes are extreme and happen quickly and those are the changes that affect the production or survival of the plants in our yards and fields.

Was the mid-February warm-up of 2017 damaging, dangerous, or just incidental? If it was endangering, which plants or crops may have been damaged?

The grapes that make the wine

Grapes are among the fruit crops that we worry about when extreme freezes occur in late winter or spring. In the Finger Lakes, Niagara County or the Chautauqua region, low temperatures alone are not usually threatening for grape production however. It’s warm temperatures followed by rapid and extreme freezes that have caused problems in the past.

When warm temperatures signal seasonal change, plant roots, stems and buds begin to absorb and hold water. If the temperatures drop gradually, the plant cells again let go of the water they acclimate. But when the temperatures drop quickly, there is no time to acclimate. Water-laden cells in the stems and buds freeze and then burst.

Growers refers to freeze-kill  and explain that all buds aren’t ruined by the same weather pattern. Some grape varieties are hardier than others and some can acclimate and tolerate extreme changes better than others.

Cornell’s Agricultural Experiment Station in Geneva maintains and studies vineyards, including which grapes are most vulnerable. In the winter of 2004-05 the weather turned suddenly from above-freezing to minus 10 degrees, killing more than 75 percent of the more sensitive grape varieties such as Chardonnay, Riesling and Pinot Noir.

Even in the same field, not every plant or every bud responds the same. Walker provided this image: "It’s as if a group of people dressed up in their warmest winter clothes and then walked into a frozen food locker for a while. Each person — like each bud — would begin to suffer at a different rate and with different consequences.

Grapes have an advantage over some other crops, he added. Cherries, for instance, have one good shot at the year’s crop, whereas grapes have primaries but also secondary shoots and buds. Depending on how quickly the temperature drops, this weather pattern could diminish production but is not likely to ruin the entire season. Walker has hope for this year’s grapes.

Landscapers and gardeners worry, too.

I spoke with several CNLPs (professional landscapers and nursery people) in recent days about their worries in response to the weird warm weather. I heard consensus on several points:

● The highest risk of damage is not from extreme low temperatures but from rapid freezes after a warm spell.

● Trees, shrubs or perennials that are planted correctly, in the right site and in the right soil, have the best odds of surviving extreme changes. (Stressed plants succumb to any threat quickest.)

● Anything recently planted (in the last couple of years) are more at risk than well-established plants.

●  Shallow-rooted plants such as some Japanese maples are more at risk than other plants.

● Plants that were well mulched will do better than plants with un-mulched root areas.

● Hardy species or cultivars, labeled USDA Zone 5 or lower, are less vulnerable than Zone 6 plants. (In response to a 30-year pattern of gradual climate change, the USDA has re-classified our region as Zone 5b or 6. However there is still risk of one harsh winter killing more tender plants.)

● Plants that were watered well last summer (in the face of an extreme drought) will fare better this winter than those that were not watered. Many consumers just think they watered well but it was insufficient for that drought. Also, few homeowners deeply watered mature trees.

Mike Frank, CNLP and owner of Chevalier Lawn and Landscaping in Hamburg, remarked that the most dangerous risk factor could be people: "They get excited that it’s spring and pull off the mulch too soon. This week I’ve had to tell customers: 'No, it’s not time for us to come out for your spring clean-up!' "

When people un-mulch, they’re making plant roots vulnerable at the highest-risk time of year. Gardeners also walk on lawns and gardens way too soon, compacting the soil and damaging delicate plant crowns including turfgrass.

Last weekend at the Home and Garden Expo in Hamburg, I heard two gardener concerns expressed many times:

  1. The bulbs and perennials are popping up way too early. Generally this will solve itself and the flowers will be fine later. When the cold resumes, nature’s anti-freeze kicks in and the plants just stall in place until warm temperatures return. Consider re-mulching, to slow the process.
  2. I see leaf buds or flower buds plumping up on my (lilac, maple, hydrangea, etc.) Will a freeze wreck the plants?  Truly I don’t know. Sometimes rapid weather changes do destroy flower or fruit production, but usually that happens later in spring. How severe, how fast the change? I think the plants will be fine. Like Walker, I have hope.

Sally Cunningham is a garden writer, lecturer and consultant. 

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