CENTERVILLE, Tenn. — Last winter is still showing up in many regions as crops affected by the arctic season are ready for harvest. Grapes are one example, as some varieties in Kentucky and Tennessee have been affected.

David Lockwood, a professor in the Department of Plant Sciences at the University of Tennessee-Knoxville, said winter injury did occur in vineyards in Tennessee as a result of numerous low temperature events interspersed with relatively warm temperatures.

"More damage appeared to occur in vineyards located in East Tennessee than in Middle or West Tennessee," he said. "The extent of damage depended on vineyard site, type of grape and vine health."

Lockwood explained sites having a south to southwestern exposure are more prone to winter damage because the extremes between high and low temperatures within short periods of time tend to be greater than on other exposures, and the vines are not tolerant of large temperature variations within short periods.

"Of the four types of grapes we grow, American bunch varieties have more tolerance to cold than the others. French-American hybrid varieties are probably second in this group, although we did experience some significant vine damage on the hybrids, especially on more exposed sites," he said.

"The Vitis vinifera grapes as a rule are fairly susceptible to cold, and we had several cold events that were low enough that damage was received. Muscadine grapes are not exceptionally cold-tolerant and I expected to see widespread damage on them."

Lockwood noted in many instances, vines started to grow in the spring and more leaf area developed, necessitating the transport of more water and nutrients from the roots to the growing points. "As the weather became hotter, causing greater water loss from the canopy, the vascular system of damaged vines could not satisfy the needs of the canopy resulting in vine collapse during the summer," he said.

He said in addition to winter cold, some areas experienced a late frost in spring that limited cropping. "Some varieties of grapes are fruitful on secondary buds and others are not. Those that are not have relatively little crop in some areas," he said. "If the vine had received some winter injury, subsequent loss of the crop was actually a good thing from the standpoint of vine survival and recovery from the winter.

"There was no stress of fruiting to interfere with vine healing. A lot of Tennessee vineyards did come through with a good crop on many varieties. Fruit quality looks good at this time and harvest is about on schedule; maybe a bit early in some places."

Jodie Morgan is a manager at Grinders Switch Winery, owned by her parents and located about an hour west of Nashville. "We are family-owned and have been here for eight years. We make all of our wines and we grow about 30 percent of what we make, which is about 5,000 to 6,000 gallons a year," she said.

"As far as the winter goes, there were some concerns especially at the coldest point, but fortunately for us we have vines that are very well established and we didn’t take too much of a hit."

Morgan said of the five varieties grown at the winery, there were a few losses but those were mainly associated with less hardy varieties or younger vines. "For the most part, everything came through really well," she said. "Our biggest concern is not so much a cold winter but a late frost."

It has been those late frosts that have created the biggest problems for Grinders Switch and other vineyards in Tennessee. Morgan said for that part of the state, it stayed cold long enough and they did not have to contend with a late frost this year.

"That’s been good for our harvest. It looks good this year and the weather has been favorable with hot days and cool nights and that’s good for grapes," she said.

As is the case with other winemakers, the need for more grapes is evident and Grinders Switch gets fruit from other growers. "There are not a lot of growers and we tend to be really picky about where we buy fruit. We always get samples from our growers because we like our quality."

Morgan said the state’s wine business is growing exponentially every year at a rate of around 20 percent annually, and more growers are needed, with the industry being worth about $11 billion.

"We currently have over 50 wineries in the state and there are more and more adding on every year," she said. "We have seen a big increase in wine visitors and that’s a wonderful thing for all of the Tennessee wineries."

For more information about the winery and vineyard business in Tennessee, go to www.picktnproducts.org and look for the Tennessee Winery Directory.