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Canopy management for premium wine production

When it comes to Ontario grape growers, Dr. Richard Smart admits he’s at a loss to understand them.

Dr. Richard Smart

When it comes to Ontario grape growers, Dr. Richard Smart admits he’s at a loss to understand them.

“I regard you all as extraordinary optimists,” said the Australian wine grape expert, referring to Niagara grape growers’ interest in, and dedication to, growing cabernet sauvignon. “Why do you do it? This is one of the coldest areas in the world to grow wine grapes and what are you growing? French Bordeaux grapes. All of the other cool climate areas grow more whites and early- to mid-season varieties. Why do you grow French Bordeaux?

“I’ve heard of the French paradox but the Niagara paradox? Give me a break.”

Dr. Smart recently visited the Niagara grape growing region and was a guest speaker at the Cool Climate Oenology and Viticulture Institute (CCOVI) of Brock University, discussing canopy management for premium winegrowing. And he couldn’t resist getting in a few jabs at the management styles of Ontario grape growers, whose plantings he described as “Hiroshima vineyards.”

“I don’t know why you let this damage happen to you,” he said as a picture of one of this season’s cold-damaged grape vines was shown on the projection screen. “Why are you complacent to this winter damage?”

Dr. Smart said he observed many local vineyards with varying degrees of winter damage, ranging from complete vine death to no death at all. But what caught his eye were the vineyards where buds and trellised vines were dead but new growth was coming again from the base of the vine which had obviously been protected from the –25 to –28˚C temperatures through hilling or snow cover.

“The vines were not killed but there was complete loss of crop,” he said. “And you have the cost of retraining those vines, which is estimated at about $1,000 per acre.”

In response to this damage and the resulting expense, Dr. Smart questioned why Niagara growers aren’t burying their fruiting vines in the soil during the winter months, thus protecting them from the frigid cold temperatures that can lead to bud and vine death. He suggested Niagara growers could continue trellising their vines but also train about four or five vines along a low wire, which could then be hilled and buried for the winter.

“If there’s a cold episode and there’s death, you can prune off the dead canes and still get part of a crop.”

Some local growers and grape experts were unimpressed with the idea, explaining that while Prince Edward County grape growers were able to succeed with protecting their vines this way, Niagara’s heavy clay soil and moisture in the spring would lead to bud rot on buried vines.

“I think we’ve just managed to talk ourselves out of the solution,” said Dr. Smart. “So, I guess you better just continue doing what you’re doing and hope global warming starts affecting winter temperatures.”

But other growers were intrigued by the idea of protecting the vines by burying them and peppered Dr. Smart with questions on the idea following his seminar. “I think you’d be better off doing this than not,” he responded.

Canopy management
Dr. Smart was also critical of the management of the Niagara area’s vineyard canopies. “Canopy management can help you grow better quality grapes in Niagara. I don’t know why you don’t do it,” he quipped, which was greeted with a roar of laughter from the audience.

He explained that canopy management basically involved the arrangement of the grape vine’s shoots, leaves and fruit and is dealt with through various tasks and tools, such as training, pruning and trellising. Canopy management is particularly valuable to Niagara because it can help maximize production of ripe grapes over a short growing season and help ripen vine wood, thus providing protection against cold temperatures, he added.

Based on an experiment conducted using a cabernet franc planting, Dr. Smart explained that opening up the vineyard canopy resulted in a doubling of yield, a decrease in the incidence of bunch rot and produced higher quality wine grapes. But shaded canopies resulted in lower bud break, decreased fruit quality and smaller fruit size, he said, adding it also led to higher disease pressure.

Opening up the canopy also obviously leads to increased sunlight interception with the fruit, said Dr. Smart, adding, “I wonder about the role of ultraviolet (UV) light on all of this.” He surmised that under increased sunlight exposure, the plant produces polyphenols, which produce a “suntan” on the grape, thus improving the fruit’s ability to handle UV and setting the grapes up to produce better quality wines.

Some growers voiced concern over the possibility of increased sunburn due to the fruit’s overexposure to the sun. “I think we need to put up with some of it (sunburn) to get the benefit of exposure,” advised Dr. Smart.

One way of opening up the vineyard canopy is through trellising. “There is no universal trellising system,” he explained, adding the method needs to be decided upon based on vineyard vigour, the grape variety, the rootstock, the soil depth, whether there is irrigation or not, the row and vine spacing and the locations of trunk posts and wires.

“The good thing about this is that you may mess it up at the start but it’s quite easy to fix it through retrofitting.”

After observing the Niagara area grape plantings, Dr. Smart suggested growers should be considering a Scott Henry trellising system rather than the currently popular vertical shoot positioning (VSP). “Scott Henry is not generally as popular and I don’t know why. You would get better results with it than with VSP.”

He added it would definitely be better than the current system he sees occurring in Niagara, which has growers re-trellising and retraining their vines every year “and spending a lot of money doing it.”

Dr. Smart added that as far as he’s concerned, summer pruning is taking place too late in the season and should be occurring when the vines have grown about 30 cm above the top wire. “If the vine is balanced, it only needs to be done once.”

He also believes shoot positioning is occurring too late and by “amateurs.” And when it comes to shoot and cluster thinning, “it’s a greater psychological than a physiological benefit. Balanced vines don’t typically need thinning.” But if you have your heart set on it, Dr. Smart suggests shoot thinning be done early when shoots are about three- to six-inches long and cluster thinning should occur before veraison. “You can have small gains but large losses with cluster thinning.”

In the area of leaf thinning, moderation is the key. “I hope you don’t do the same thing as they do in New Zealand and California,” he said as he showed a slide of a completely denuded vine with bare clusters of grapes. “I think they’ve been venting their anger on the poor vines.”