Surviving Challenging Environments
ASEV conference addresses vineyard management tactics for difficult locations
Be it too hot, too cold, too wet or too dry, many locations are not ideal for growing grapes and making wine. Yet people are growing grapes and making wine in all 50 states, whether they face difficult environments or not. Of course, even the best places to grow grapes have years that are challenging. On June 27, the final symposium at the 65th national conference of the American Society for Enology and Viticulture in Austin, Texas, examined different aspects of growing grapes and making wine in challenging environments.
Sara Spayd, professor in the Department of Horticultural Science at North Carolina State University, introduced the symposium by saying, “We are not talking about challenging environments within the winery, so the program’s focus will be on some of the viticultural and enological issues arising from environmental challenges.”
In the vineyard
The major problems with growing grapes are related to sunlight, temperature and water. Growers can use various management options to address those problems, including site selection, vineyard design and viticultural practices within a growing season. Ed Hellman, a professor of viticulture at Texas Tech University who has a joint appointment with Texas Cooperative Extension, examined the different challenges facing growers in detail.
If the problem is insufficient sunlight, for example, the grower will need to take that into consideration when planning the design of the vineyard. Slopes should be south-facing, rows planted in a north-south orientation, and the vine spacing and training system both should be appropriate for the anticipated vigor of the vines to be planted on the site. The fruit zone may need to be up high and exposed, and in-season viticultural practices may include shoot positioning, basal leaf removal, hedging and reflective mulches.
On the other hand, if the challenge is excessive sunlight (leading to excessive heat), or a heat wave with temperatures at 104° F or higher for an extended period, the grapes may have a lower anthocyanin concentration, reduced malate and total phenolics, “cooked fruit” flavors and sunburn due to excess light and heat. If the potential for excessive heat or sunlight is known before the vineyard is planted, the grower can find a site with an east or north slope aspect, plant cultivars that are more tolerant of heat, orient rows in a northeast-southwest direction to reduce solar heating, use a trellis system with wider cross-arms on VSP catch wires to encourage partial shading of the fruit zone, and consider using sprawl or high-cordon training with no shoot positioning.
During the growing season, growers can prune to a higher shoot density (five shoots per foot), shoot position only on the shaded side, use a modified VSP system with wider cross-arms, and plant a cover crop, stubble or mulch to avoid the re-radiation of solar heat. Other within-season practices may include delaying véraison so the fruit will mature when the temperatures are cooler as well as increasing the crop load.
Cooler climates with insufficient heat can lead to grapes with incomplete fruit maturity. Consequently, it’s important for growers to select cultivars that mature early and require fewer heat units to ripen. Vineyards should be south-facing with north-south row orientation (similar to the insufficient sunlight vineyards) and situated at lower elevations. Training systems can have narrow canopies, a high fruit zone (such as sprawl or GDC), or a low VSP can be used to take advantage of reflected ground heat while recognizing that there will be more risk of frost. Within-season practices may include shoot positioning and basal leaf removal to increase cluster light exposure, and the vineyard floor may be clean cultivated.
Regions with excessive cold weather present challenges for vines in the dormant season as well as the growing season. Very low temperatures can lead to trunk, cordon and bud damage resulting in reduced, inconsistent yield and asynchronous fruit ripening. Growers should avoid south- and southwest-facing slopes, as they often warm earlier in the spring and may be more prone to spring frosts. Cold-hardy varieties should be planted on mid-slopes for warmer temperatures, with high fruiting wire training and multiple trunks. Viticultural practices may include delayed pruning or double pruning, the use of wind machines, careful balancing of the crop load, canopy management for light exposure, water management to encourage early acclimation and field and/or winery sorting of fruit to increase uniformity.
Insufficient water obviously has an impact on both grapevines and their grapes. Grapevines may have reduced shoot growth and leaf size, reduced carbohydrate reserves and earlier shoot maturation. The fruit will have smaller berry size, lower yield, incomplete ripeness and a higher concentration of phenolics. Vineyard design will have to include developing a water source (or finding a different site), use drought-tolerant rootstocks and a low-vigor trellis system.
In contrast, regions with excessive water can have too much vine vigor, with concomitant shade problems. Acclimation may be delayed, with reduced cold hardiness resulting. Berry size may be larger, clusters tighter, and fruit may be prone to berry cracking, increasing the potential for bunch rot diseases. Measures must be taken within the viney ard to reduce vine vigor through wider vine spacing, the use of permanent competitive cover crops and training systems to accommodate high vigor. Disease and canopy management are most important.
In summary, Hellman noted that environmental factors interact (light exposure, temperature and water), and growers must integrate the management of the whole system.
Variety development for challenging environments
Peter Hemstad, grape breeder at the Horticulture Research Center at the University of Minnesota, has experienced some of the most challenging of environments for growing grapes. According to Hemstad, Minnesota had 53 days with temperatures below 0° F during the winter of 2013-14, and to compound the difficult growing conditions, some regions received more than 13 inches of rain in June 2014. Given a climate with those challenges, Hemstad has specific goals he is looking for when breeding grapes: cold hardiness, disease resistance, growth habit, productivity and (of course) wine quality.
Or course, Hemstad is not the first grape breeder in Minnesota. While Elmer Swenson is often referred to as the father of cold-hardy grape varieties in Minnesota, the basis of his grape crosses was a variety known as Beta. That grape was a cross of Concord and Carver (vitis riparia) made by Louis Suelter in 1881. Swenson worked at the University of Minnesota from 1969 to 1978, and he introduced several varieties including Edelweiss, St. Croix, Sabrevoix and Briana.
Since 1996, Hemstad and the University of Minnesota have released four major cold-hardy varieties: Frontenac (1996), La Crescent (2002), Frontenac Gris (2003, which came from a mutation of a single bud of Frontenac in a research plot) and Marquette (2006). Introduction of these varieties and others have permitted a wine industry to develop in the northern Midwest and New England as well as other cold climates such as northern New York and Quebec, Canada.
In the winery
Challenging environments in the vineyard can result in grapes that present additional problems for winemakers once those grapes arrive in the winery. Green, herbaceous flavors; high pH, high acidity (or both high pH and high acidity); difficult malolactic fermentations, and color and phenolic issues are some of the major problems that winemakers must handle.
Additional speakers from ASEV’s Winemaking for Challenging Environments Symposium addressed ways to improve must and wine quality in the winery, and these topics will be addressed in a follow-up article in Wines & Vines.
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