Winery owner Brent Helleckson’s hands flew among his budding grapevines, pruning off bits of cane as a spring breeze ruffled the plastic tape keeping the vines trellised to wires. Cut spurs, their ends as green as the grassy aisles between rows, glistened with sap flowing to the buds that had survived the winter. On the other side of Western Colorado’s North Fork Valley, snow lingered on mountain peaks, a reminder of the wintery weather that circumscribes the vineyard’s operations. “In theory we’re done with frost now,” Helleckson said. “But I wouldn’t bet on it.”
In a warming West, areas where wine grapes are growing at the limit of their cold tolerance may see a respite from frigid, plant-damaging winters. But other changes, including droughts, erratic swings in temperature, and earlier ripening may make viticulture more difficult even in cooler locations like Western Colorado. Warmer areas, meanwhile, including parts of California, may become too hot for the high-quality wine grapes that thrived there in the past. Thanks to the resilient nature of grapevines and the growing demand for regional wine, experts don’t expect vineyards to disappear from the West. However, which varieties are grown where, and at what cost, will likely continue to shift in the coming decades.
Here in the North Fork Valley, cold temperatures, high elevation and volcanic and calcium-based soils result in “nicely acidic wine with lots of intense fruit flavors,” says Helleckson, who produces merlot, chardonnay, gewürztraminer and other wines at Stone Cottage Cellars. But that cooler climate carries risks: winter temperatures below zero degrees Fahrenheit can freeze vine trunks, forcing them to regrow from the roots, which takes years. In the fall, sudden temperature drops — the sort of variability that is expected to increase with climate change — can be particularly damaging if plants haven’t yet acclimated to colder weather. Vines desiccate slightly to allow internal water to freeze without bursting cells, for example, and the plants pump carbohydrates down to their roots, stockpiling energy to fuel spring growth.
The start of spring has been advancing across the United States; Helleckson has noticed early warm spells at his vineyard too. That can pull vines out of winter dormancy before the threat of frost is past, leaving buds susceptible to freezing. While cherries, peaches and other trees won’t fruit at all if a spring frost kills their blossoms, grapes get a second chance. A single freeze can kill the primary shoot within the bud but leave behind a secondary shoot, which yields about half the normal crop. That’s better than nothing, says Horst Caspari, Colorado’s state viticulturist and a professor at Colorado State University’s Western Colorado Research Center in Grand Junction, but growing grapes is, after all, a business: “We do want the full crop. We don’t want to be cropping on secondaries.”
Warmer springs also mean the mountain snowpack melts more quickly. That can send runoff downstream before grapevines need it most, just after they’ve leafed out. If the timing is off, growers might need to start drawing on stored water for irrigation earlier than they typically would. “Once you start pulling out of the reservoirs,” Helleckson says, “there’s only so many days of water in there, and then you’re done.”
Drought and heat waves are already a problem for vineyards in other parts of the West, including parts of California, according to viticulture professor Markus Keller at Washington State University in Prosser. Although wine grapes are relatively drought-tolerant and they will still grow in hot, dry places, their quality can suffer, a prospect that could have major economic impacts: In 2015, California produced more than 80 percent of the wine made in the U.S. and the state’s wine grape crop was valued at $2.5 billion.
The quality of wine grapes is also affected by shifts in ripening times. In the last two years, wine grape growers in the Western U.S. have harvested their crops a month to six weeks earlier than what was typical a quarter of a century ago, says Gregory Jones, a wine climatologist at Southern Oregon University in Ashland. That change affects both the character of the fruit and the flavor of the wine it produces: It’s common to end up with less acidic grapes that have a higher sugar concentration, which can result in higher alcohol content. Winemakers can manipulate those qualities during production, but it’s unknown how artificial additions and subtractions affect the nature of wine, Jones says.
To keep producing top-notch grapes, viticulturists may need to relocate their operations. In California and Washington, for example, some growers are already planting vineyards further north or moving up in elevation, Keller says. They can also combat the heat by hanging shade cloth or positioning rows on a sun-sheltered north-facing slope. Another option is to grow varieties that are better suited to a warmer or drier climate, though that can become a moving target as the climate continues to change.
Growers may also have to cope with a shifting suite of insects and ailments. While moisture-loving pests like fungi or mildew may decline in areas that become warmer and drier, other bugs and diseases will likely take their place.
At Stone Cottage Cellars, Helleckson is planning to grow grapevines planted on grafted rootstock at a cost of several thousand dollars per acre to avoid the ravages of an aphid-like insect called phylloxera, first discovered in Colorado in late 2016. Phylloxera — which sucks sap from the roots of certain grapevine species while injecting a plant toxin, eventually killing the vine — probably didn’t get a foothold in Colorado because of climate change, says entomologist Bob Hammon, an agricultural extension agent with Colorado State University who is based in Grand Junction. But how growers protect their vineyards from the pest could offer a blueprint for handling future challenges. “Is the Colorado wine industry going to crash?” Hammon asks. “No, it’s going to adapt.” That will be true of the West’s wine industry overall as growers and producers face the realities of climate change.
This story first appeared in High Country News.
Photo credit: Brooke Warren, High Country News