A view of the south shore of Lake Okanagan in British Columbia. (courtesy Ben Lawson)

A view of the south shore of Lake Okanagan in British Columbia. (courtesy Ben Lawson)

British Columbia growers may have the basic information about soil and climate when it comes to developing vineyards, but greater attention is needed to matching varieties with location, and then finding the specific clones of the variety that will perform best, according to a noted specialist in soil science and plant nutrition.

“I think they have to figure out the varieties. They don’t have any information about clones,” said Dr. Daniel Roberts, principal of Integrated Winegrowing LLC in Sebastopol, California.

Roberts, who is planting his 125th vineyard this year, spoke to growers attending the annual B.C. Wine Grape Council meeting in Penticton this summer on the topic Using Climate and Soil Data in Vineyard Development.

Roberts discussed soil and climate factors that are critical in vineyard development.

Soils in British Columbia’s Okanagan Valley are very different than anything he deals with in California, but the soil basics are still the same, Roberts said in an interview following his presentation. “Do I have good drainage? Do I have any nematode issues? Do I have any toxicity? We look for the same thing.”

The dominant cation of Okanagan soils is calcium, which Roberts said gives the soils a unique profile on par with the limestone soils around Paso Robles and King City along California’s Central Coast, one of the state’s fastest-growing wine regions. The Okanagan soils are glacial till, but some of the rocks from further north in British Columbia are limestone, so they have high calcium and their cation exchange is very high, Roberts said.

Key climate factors to bear in mind include frost and the potential for winter kill, degree-day accumulation, diurnal temperature change from veraison through harvest, and wind.

Roberts said he talked to B.C. growers about wind and what to watch out for. “I showed them their rainfall patterns, and ours. I showed them their growing degree-days versus ours.”

His conclusion?

“Kelowna has a climate very similar to my best Pinot Noir vineyard on the Sonoma Coast. So, for me, that said you guys can grow world-class Pinot [Noir] and Pinot Gris and Riesling,” he said.

He feels Chardonnaythe variety that catapulted Kelowna’s Mission Hill Family Estate and the entire Okanagan to prominence in 1994is a contender for vineyards throughout the valley, even more so than Pinot Noir.

Cabernet Sauvignon

A weak spot, however, is Cabernet Sauvignon.

He thought that in the southern Okanagan Valley, they didn’t get enough heat to ripen Cabernet. “They barely got 2,800 degree-days in a warm year; that’s just barely getting Cabernet ripe,” Roberts said.

But the range of climatic variation from north to south within the long, narrow Okanagan Valley leads to regional variation and the need to closely analyze sites to pick varieties that can work.

“I think they have potential for high-end Merlot, Cabernet Franc, Malbec, things like that,” he said of the southern end of the valley. “In the midregion, I tasted some great Syrahs and Merlots and Chardonnays.”

The challenge is finding the right clones to perform under given climatic conditions, especially in some of the more marginal areas.

“Cabernet Clone 7 won’t do it,” he said, referring to one of the workhorses of California vineyards, also known as the Wente clone. “They need to look at other clones coming out of France They might be able to play with clones like 169, which can, in a cooler area, get ripe at a lower Brix.”

This is what many growers in the valley have done, said Dick Cleave, a vineyard consultant based in Oliver. Vineyards he oversees also have clones 15, 191, and 339.

Fussy

Cleave acknowledges the challenges that Cabernet Sauvignon presents, but isn’t as pessimistic about growing the variety in British Columbia as Roberts is.

There are more than 755 acres of Cabernet Sauvignon planted in the province, and the variety was the fifth most significant by harvested tonnage last year. Cleave tends to harvest his own at 25.5 degrees Brix, and in some years has brought it in at more than 28 degrees.

“You have to be really, really fussy with it. It’s an expensive grape to grow, but if you put it on the right rootstock in the right locations, you can do it,” he said. “You need it on Riparia Gloire, you need it on sandy soils, and on drip irrigation.”

He limits yields in his own vineyard, on the east side of the valley facing Oliver, to about three pounds per vine.

A handful of vineyards in the province are also using Blattner clones, disease-resistant selections that require significantly less heat units to mature; there are approximately 100 acres of them planted.

Cleave’s close management of his vines and the adoption by other growers of the Blattner vines underscore the growing appreciationand responsivenessgrowers have to Okanagan conditions.

“I think they have an opportunity to put British Columbia on the map, and I think there are some winemakers up there now who have some real skills,” Roberts said.

While he feels the industry could benefit from broader clonal trials, he heaped generous praise on the work of Dr. Pat Bowen and her team at the Pacific Agri-Food Research Centre in Summerland.

“She actually does research in vineyards, and her information actually is practical and actually has meaning to the farmers,” he said. “That’s the first place in the world I’ve actually seen a researcher doing research in vineyards and helping growers.” •