Vineyard pruning trials underway in Weslaco

Interest growing in wine vineyards in South Texas

WESLACO  —  As the interest in wine vineyards grows in South Texas, the Texas A&M AgriLife Extension Service is developing information that could prove useful to future growers, including how best to prune.

“Properly pruning a vineyard is one of the most important steps in growing an abundant, high-quality and healthy crop of grapes,” said Dr. Juan Anciso, a fruit and vegetable specialist at the Texas A&M AgriLife Research and Extension Center at Weslaco.

“Pruning forces more production,” he said. “By cutting back a vine, bigger clusters of grapes are produced on bigger wood, as opposed to smaller clusters on thinner vines.”

In a small demonstration field plot south of Weslaco, Anciso is growing white and dark grapes using four different pruning methods.

“We’re comparing the four methods of pruning that I refer to as the European, Texas, New York and California methods,” he said. “They each have longer, more descriptive names but for the sake of simplicity, I’ve given them names based on where the methods were developed.”

The European, or old style, of pruning allows the plant to grow to only 4 feet. Its vines are then strung along a single wire to make a simple t-shape, Anciso said. The Texas and New York methods are allowed to grow taller. Vines are strung along two wires running parallel to each other. The California method is much like the single-strand European method, but the plants grow at a taller height to making harvesting easier

“Each method has its advantages and disadvantages,” he said. “What we’re trying to determine is which method is best suited to our climate and soil type.”

Anciso is also evaluating a wild grape rootstock called Dogridge on Blanc du Bois grapes, a relatively new white grape variety.

Texas is the nation’s top producer of wines from Blanc du Bois grapes, with more than 20 commercial wineries making vintages from these grapes, according to the Texas Wine and Grape Growers Association. The state currently has more than 150 acres of the grape in production.

“Dogridge seems to be more tolerant to our alkaline soils and it shows some tolerance to cotton root rot, a soil-borne fungal disease that until recently severely limited grape production in this area,” Anciso said.

To evaluate the four pruning methods, Anciso planted 60 plants in February 2011 – three plants per pruning method replicated five times.

“It usually takes two years for plants to produce grapes, but we harvested our first crop in one and a half years,” he said. “This summer we’re harvesting our second crop, and while we’re still crunching the numbers, it’s obvious that the New York and Texas methods of pruning produce the highest yields by far. With two lines of vines growing from each plant, there is obviously more wood in the same area as compared to the European or California methods.”

While yields of the New York and Texas methods may be higher, both pruning and harvesting are much more labor intensive.

“We have two commercial vineyards here in the Lower Rio Grande Valley,” Anciso said. “The Monte Alto Vineyard uses the California method. There’s less pruning involved, harvesting is easier and overall management is easier. The other, Jaber Estate Winery, uses the New York method. Yields are higher but both pruning and harvesting are much more labor intensive.”

Regardless of the method used, vineyards are pruned annually while the plants are dormant.

“After the summer grape harvest, the plants are watered and fertilized,” he said. “By October, leaves start dropping naturally and by December they are all gone. Pruning is done in January before leaves and buds start to sprout in February.”

Pruning is more labor intensive than harvesting, Anciso said, but must be done religiously.

“While homeowners may get away without pruning, it’s a must in commercial vineyards. Without pruning, you end up with a tangled mess of unproductive plants.”

Anciso began the pruning demonstration plot with Fritz Westover, a former AgriLife Extension viticulture specialist in Houston who now works in California.

“Mr. Westover was kind enough to assist in the second harvest of our demonstration plot in Weslaco recently,” Anciso said. “It’s important that we develop viticulture data specific to South Texas because our first two commercial vineyards here are doing well and others will likely soon follow.”