Great Wine Sees the Light

By Katie Meyer
SPARK Program

Justine Vanden Heuvel has found that growing grapes on trellis systems maximizes light to the fruit, which yields more grapes and heightens their flavour.
PHOTO BY MARTIN SCHWALBE

When it comes to growing grapes for winemaking, researchers say let there be light.

Justine Vanden Heuvel, a PhD student in the Department of Plant Agriculture, has found that growing grapes on trellis systems maximizes light to the fruit, yielding more grapes and heightening their flavour.

She's worked with more than 2,000 vines, alongside advisers Helen Fisher of the Vineland Research Station and Prof. Alan Sullivan, to achieve the ultimate trellising system.

"I hope my research will give grape growers in all cool-climate areas a better understanding of how to grow grapes that will make high-quality wine," Vanden Heuvel says.

Historically, it was thought that a higher yield of grapes meant lower-quality fruit. But in the 1980s, a New Zealand researcher reported that the amount of fruit on a vine was not actually an indicator of quality. Since then, emphasis has turned to controlling the vigour of a vine, which is the size of the vine and its productivity. Trellising is one way of doing so; it involves manipulating the architecture of the vine to control vigour and increase the light exposure to the grape clusters.

High fruit quality depends on light exposure on clusters because light allows the fruit to accumulate sugar (sugar is an important measure of fruit quality because it translates directly to alcohol level fermentation). Vanden Heuvel has confirmed that high yield and high fruit quality can exist at the same time.

Now, she's examining the vigour of the vine and yield and the quality of the fruit and the wine that comes from it. She's testing the trellising systems for two cultivars, the white grape Chardonnay and the premium red wine grape Cabernet franc.

Vanden Heuvel's comprehensive study includes four traditional-type trellis systems and two of their modern counterparts. She is examining the density of the vine using a light sensor to measure the penetration of light into the internal vines of the plant. The research includes testing the effectiveness of alternative contemporary trellis systems.

She has discovered that modern trellis systems increase grape quality because they allow more light penetration to the vines.

Traditional trellising zones tend to concentrate the fruiting zone - where the fruit grows on the shoots, says Vanden Heuvel. Her research compares the traditional trellising systems with the newer systems in the Niagara Peninsula.

"I'll be able to tell grape growers why certain trellising designs function better for both productivity and wine quality," she says.

Vanden Heuvel was invited to present her current findings to the American Wine Society in South Carolina in November.

This research is sponsored by the Ontario Grape and Wine Adjustment Program, the Ontario Ministry of Agriculture, Food and Rural Affairs, the American Wine Society Educational Foundation and the eastern section of the American Society of Enology and Viticulture.