As mentioned in my first quarterly update, the vines are at risk from frost during the spring months, and as fate would have it – that’s just what happened. On the morning of April 29th, we had a frost event. Of the three vineyards we farm, only one was seriously affected. Kenridge Vineyard, which adjoins our property here at the winery, was unaffected. This vineyard is located on a slope that allows cold air to drain away from the vines. Glenway Vineyard, located at the winery, was only mildly affected with only a few of our new vines being damaged. These vines have their growing shoots located very close to the ground where the coldest air settles. Our third vineyard, Chapelle Charlemagne, was not as fortunate. This vineyard is also located on a slope, but the tree lines and other topography features of this site are such that cold air is trapped at the bottom of the slope. The Chardonnay and Cabernet Sauvignon vines, which are planted at the top of the hill, were generally undamaged. But at about the halfway point down the slope, the tender shoots on Cabernet Franc vines were frozen. Shoot tips, as well as early grape clusters, were severely damaged. Our initial estimates forecast crop losses to be at around 50%. These vines will ultimately push new shoots from secondary and basil buds, but on vinifera vines, those secondary shoots are usually un-fruitful. This new growth will however provide fruitful buds for next year, but the damage has been done for the current vintage.
Adding to that, a second frost event occurred on May 10th. This was a wide spread event that affected vineyards from as far south as Charlottesville, and northward into Loudon County. Many vineyards incurred total losses, while some were completely spared. Our Kenridge site was again undamaged, but Glenway had spotty damage, with losses in Viognier at around 30% and Vidal Blanc at about 80%. Chapelle Charlemagne was also affected, although less severely than on the April 29th event.
Such is the life of a winegrower. Forecasters generally do a good job of warning us about these damaging weather events; but if vineyard owners have not invested in some form of frost protection, all the forecasts in the world won’t be of any help. So, what can be done? The best form of frost protection is to plant on sites that are less susceptible to frost. That is, sites that allow for cold air to drain away from the planted areas. This requires proper planning prior to planting. Temperature readings must be taken around the site with careful observations on cold mornings to locate areas where cold air accumulates. Careful selection of grape varieties must also be made to avoid planting frost sensitive varieties in questionable areas of the site. High wire trellis systems such as Geneva Double Curtain can be utilized to raise the growing points of the vine above the potential frost line. A matter of inches can make the difference between frost avoidance and absolute devastation. On established sites where this planning was not done, or if the risk factors were determined to be low enough to plant vines in these frost-prone locations, wind machines can be installed. These machines (some of which resemble windmills) can be utilized to stir up any colder air below with the warmer air above, thereby raising the overall temperature of the site. In the absence of these machines, some growers will even hire helicopters to hover over their site to create the same effect as wind machines. The downside of this approach (aside from the cost) is the need for helicopters to leave the site for refueling, which in turn leaves the grower unprotected during the helicopter’s absence.
Here at Rappahannock Cellars, we are investigating the investment in wind machines to avoid future damage. The cost of these machines however, ($15-25K for a machine that covers 6-10 acres respectively) is a difficult pill to swallow for a site that is only sporadically at risk to frost. Murphy’s Law would dictate that once installed, we would likely never need them. But if they saved us from only a single devastating frost, they have paid for themselves several fold.
Meanwhile the growing season continues to progress. As of the writing of this update, shoot growth in most varieties has reached the top wires of the trellis. Shoot thinning, a process of selectively removing shoots along the cordon to a specific density (shoots per foot of cordon) is complete, and most varieties have completed bloom. We are now at a growth stage known as ‘fruit set’. After a successful bloom and correct pollination of the flowers, the grape berries begin to form. At this stage, several time-critical tasks must be performed. Shoots that remain outside of the catch wires must be tucked into them and oriented in an upward direction. At the same time, leaves will be removed from around the fruit to increase light exposure and air flow in the fruit zone, reducing the potential for diseases to develop. This step is especially important for red varieties. Exposure to light will facilitate the degradation of a particular chemical compound in grapes called methoxypyrazine [MP]. These pyrazines are what contribute the undesirable vegetal or ‘bell pepper’ characters in red wines. Red fruit at harvest time could be fully ripened in all respects (sugar, pH, color, etc) but if high quantities of MP’s remain; red wines will express unripe characteristics. There is no way to correct this situation in the cellar and it is completely dependent on the prudent winegrower to assure these qualities are not present in their fruit. But is a delicate process; it must be done early enough and not so completely as to cause sun burning of the grapes, which could cause ‘cooked’ flavors in some of the more delicate white varieties – not to mention significant crop losses. This is but one example of the fact that fine wines are first made in the vineyard.
‘Till next time,
Cheers!
-Tom
