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A rush to ripen as growing season enters final months

By Dave Buchanan

Grand Valley grapes are rushing to catch up with a summer that’s soon to end.

The catching up comes as a result of a long, cool spring, which included a frost at the end of April that killed some of the valley’s grape crop and set back the rest.

That, in addition to damage still lingering from the killer cold weather in 2009, has dropped the valley’s prospective grape crop by 30 percent or more.

“It was the 27th of April to the first or second of May and May first might have been the most severe,” said Horst Caspari, state viticulturist at Colorado State University’s Western Colorado Research Center on Orchard Mesa, of the spring frost felt by most grape growers.

And maybe you were wondering why your tomnatoes are so slow to ripen.

Blame the frost and cool spring for that, too.

Caspari said the severity of the frost was compounded because it came just as most of the grapes were heading into bud break, when the first tiny green shoots emerge from the grape buds.

It’s a time when the young growth is particularly susceptible to cold damage.

“At least one vineyard really got hammered and every day I hear from more and more growers that they expect a very light crop or no crop at all,” Caspari said.

He estimated the valley overall lost about 30 percent of its grape crop.

“When we get a late frost like that during bud break, all the cards are off the table,” Caspari said. “It all depends on when they push” their new growth.

Grape growers always are watching their crop, fearful that if bud break occurs too early, the young shoots may suffer spring frost damage.

However, if bud break occurs too late, the grapes may not have enough time to fully ripen before the summer ends.

That leaves the grower having to decide either to pick early (usually resulting in undesirable green or vegetal flavors in the finished wine) or letting the grapes hang longer and risking a fall freeze.

Normally, losing 30 percent of a crop wouldn’t be disastrous because growers usually drop or prune 10 to 15 percent or more of their crop during the summer.

This “green-cropping” concentrates the vines’ nutrients in the remaining grape clusters and improves the quality of the remaining fruit.

But as you drive around the valley, you’ll notice there still are many signs of the continuing recovery from the 2009 sub-zero temperatures that killed up to 75 percent of the valley’s vines.

“Yeah, we’re still behind but how much is hard to say right now,” said Neil Guard of Avant Vineyards on East Orchard Mesa. “When it gets hot like it’s been lately things really catch up fast.”

Caspari agreed, saying grapes that were 100 growing-degree days behind earlier this summer now are about 30 degree days behind their normal development.

“That’s about a week,” Caspari estimated.

Growing degree days, which are tied to temperatures 50 degrees and above, are calculated to track a plant’s maturation.

“The cool spring in some ways was good because it delayed the vines and gave us more time to get some pruning done,” Guard said. “On the other hand, it means we’re a little behind going into August and all we can do is hope for a nice fall, meaning one without an early frost.”

Guard said some of his cold-hardy varietals such as Cabernet Franc and Tempranillo are starting veraison, the transition from unripe, green grape berries to deep blue, purple or black.

“But that means I spent the entire weekend out in the vineyard, putting up netting,” Guard said. “I hate putting up netting but a flock of birds can easily wipe out a whole year’s crop.”


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