Pre-Christmas Freeze and Impact on Grapevines
By: Imed Dami, HCS-OSU
On December 23-24, Ohio experienced the coldest temperatures of the year 2022. Temperature lows ranged between 3F and -13F (see map). Statewide, the lowest temperatures occurred in West central Ohio and ranged between -9 F and -13F. In central Ohio, minimum temperatures ranged between -5F and -10F. In southwest, temperature dropped to -7F to -12F. In southeast, 3F to -6F were recorded. In Northwest, temperatures ranged between -3F and -11F. Northeast (majority of vinifera grape acreage) experienced the mildest temperatures ranging between -2F and -6F. At our research vineyard in Wooster, we recorded -7F on December 23, 2022.
To have a preliminary assessment of cold injury, we collected canes from our most cold sensitive vinifera varieties. We also collected a cold hardy hybrid, Frontenac blanc for comparison. Our findings were disappointing with higher-than-expected cold damage across the board. Table 1 summarizes cold injury of primary and secondary buds from 8 varieties. In vinifera primary bud injury ranged between 87% and 100%. Frontenac blanc sustained only 5% primary bud injury. Our results suggest that cold damage of vinifera varieties could be more severe than expected across the state. Hybrids (with LT50 of -13F or lower) should have minimum to no injury from this cold event.
The extensive cold damage of vinifera varieties is puzzling. In late November, buds showed a good level of cold hardiness. For example, Chardonnay had LT50 = -7.7F. In December, low temperature of -7F was recorded in that vineyard in Wooster. So, at that temperature, we should have 50% or more bud survival. But, that was not the case and we had 10% primary bud survival (see Table 1). One way to explain this discrepancy is that vines lost cold hardiness in December. This is possible since we had a mild December with mean temperature 3F above the 30-year average (Figure 2).
We still have a few weeks to go with winter weather and potential damaging temperatures are still possible. Growers should be mindful of that and bud assessment, before pruning, is recommended. Pruning adjustment is definitely needed this year.
Figure 1. Minimum temperatures on December 23-24, 2022. Note that minimum temperatures ranged between 3F and -13F. Source: Dr. Aaron Wilson, OSU state climatologist.
Table 1. Bud injury of 8 grape varieties exposed to -7F on December 23, 2022. Wooster, OH.
Species |
Variety |
Clone |
Primary bud injury (%) |
Secondary bud injury (%) |
V. vinifera |
Arneis |
FPS 01 |
100 |
100 |
|
Cabernet franc |
FPS 11 |
90 |
82 |
|
Chardonnay |
FPS 37 |
90 |
50 |
|
Dolcetto |
FPS 02 |
100 |
100 |
|
Malvasia |
FPS 03 |
100 |
100 |
|
Sauvignon blanc |
FPS 27 |
87 |
67 |
|
|
|
|
|
Hybrids |
Frontenac blanc |
|
5 |
2 |
|
Regent |
|
94 |
67 |
Figure 2. Monthly mean temperature deviation from the 30-year average in 2022 in Wooster. Bars above 0F means temperature was above the 30-year average. Bars below 0F means temperature was below the 30-year average.