Trends seen on zone map have long been evident to Virginia's growers
By Alison Laurio -- firstname.lastname@example.org
WINCHESTER -- The warmer temperatures in some areas of Virginia evidenced in the new Plant Hardiness Zone Map have been small changes, but they are not news to the state's winegrowing professionals.
"There's an expectation of some continuing patterns of warming in Virginia, in the U.S. and globally, and it could have an impact on vineyards in Virginia," said Tony K. Wolf, professor of viticulture at Virginia Tech and director of the school's Agricultural Research and Extension Center in Winchester. "We've already seen some of those changes over the last 10 years.
"In our vineyard here in Winchester, we haven't seen zero degrees since 1994, but we have a very good site."
Even in the 1980s and 1990s, growing the Merlot grape was not recommended because winters were too cold, he said.
"Since then, the acreage of that particular variety has increased greatly," Wolf said. "It's probably our No. 4 variety produced in the state right now."
Going back even further, chardonnay and cabernet, now thriving in Virginia, also were just not grown here, he said.
"The winter cold was the chief reason," Wolf said.
Warmer weather also has opened up the western and southwestern parts of the state for vine production, he said.
"Around Blacksburg 15 to 20 years ago, there were no wineries in that area," Wolf said.
Warmer temperatures are bringing some "disfavored" effects, like Pierce's disease, he said.
"It's a bacterial disease of grapes, and it's lethal to the vines," Wolf said. "Historically, it's been in the southeastern part of the state, and we've seen a movement toward the west and toward the north. Even the Richmond areas are at risk."
It does not prevent growing, but it impacts the profitability of growing, he said. And the industry's response in the southeast has been to plant more muscadines, a different genus of grape that is tolerant of Pierce's disease.
"That particular disease and other diseases like that can be favored by warmer weather," Wolf said.
It has been warmer since the turn of the century, and particularly in 2007 and 2010 it was "unusually warm," he said.
"As growers, we know some varieties grow better in cooler weather and some are well suited to warmer areas," Wolf said. "As climate changes, we have an opportunity to change the portfolio of varieties grown here."
Cooler-weather loving Riesling was the No. 2 grape in acreage in the mid-'80s, but it is now down "well below No. 10," he said.
It takes time and money to establish a variety, and it takes "a pioneering wine grower," Wolf said.
Growing a new vine to the production stage can take three to four years, and some red varieties need an additional year or two until they're aged and released, "so it's a long-term investment," he said.
Moisture, or the lack of it, is an additional factor for vineyards. Although about 25 percent have irrigation systems, "there's not a lot you can do about rainfall," Wolf said.
Cover crops, planted among vines, help soak up heavy rainfall, and root stocks that favor a smaller vine can produce less canopy foliage, which allows for more sun exposure and can discourage fungal diseases, he said.
Some climate changes are hard to quantify, but not all.
"One thing we've measured and seen with the warming climate is we used to have bud break on the 21st of April," Wolf said. "That date has moved almost two weeks to the 7th of April -- just over the last 10 to 15 years."
The extra growing time provides no benefits, he said, but it does give growers a longer time to combat insects and diseases and worry about getting the crop in safely.
"One of the hallmarks here is variability," Wolf said. "Over the last 25 years, I have seen just about everything you can imagine. We plan for droughts and we plan for the occasional 10-inch rainfall. I don't see that variability really changing."