Interpreting the Graphs and the Table
If the temperature lines in the graph (top two blue lines) cross over the critical temperature lines for buds, then damage has likely occurred. Please review the Resources in the right navigation bar for information on managing cold-damaged vineyards.
When we are at or approaching bud break, we will not be able to run exotherm analysis in grapes any more. In previous years we have included the critical temperatures for several different varieties during the period leading up to bud break. Since every variety responds differently to cold, this should be used only as a rough guideline.
- Cabernet Sauvignon at first swell sustained no damage down to 25°F.
- Merlot at full swell showed slight damage to the buds, phloem, and xylem at 25°F. More serious damage to the phloem and xylem occurred at 23°F.
- Chardonnay at budbreak showed slight damage to the buds and phloem at 27°F. More serious phloem and xylem damage occurred at 25°F. Buds were seriously affected at 24°F.
Preventing Cold Damage in Grapes:
- Protecting Grapevines from Winter Injury (PDF)– PNW #603E
- 2012 USDA Plant Hardiness Zones – The best way to prevent cold damage is to not plant in areas prone to it. Use this interactive map to determine if your area is at high risk.
Assessing Cold Damage in Grapes:
- Assessing and Managing Cold Damage in Washington Vineyards – WSU #EM042E
- ESPAÑOL – Evaluación y Manejo del Daño por Frío en los Viñedos de Washington
- Winter Freeze Damage and Vine Fruitfulness (PDF): Why does cold damage impact yield? – WSU Whitepaper
- Anatomy of Winter Injury (PDF) – Cornell University
Responding to Cold Damage in Grapes:
- Effect of Pruning on Recovery and productivity of Cold-Injured Merlot Grapevines – AJEV 2007 58:351-357
- Vine and Vineyard Management Following Low Temperature Injury – ASEV 2000 Cold Hardiness Workshop