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College of Food, Agricultural, and Environmental Sciences


Managing injured vines after frost - May 2023

Monday, May 01st, 2023

By: Imed Dami and Maria Smith, HCS-OSU

Statewide frost events occurred on April 24-27 (Table 1). Early budding varieties had already broken buds or were at a more advanced shoot development, and thus sustained frost damage. At the OSU research vineyard in Wooster, temperatures in a shielded logger at 5ft high measured 32F on April 25 and 34F on April 27. However, when we measured the temperatures in proximity to the fruiting spurs, we recorded temperature between 27.5 °F and 30.2 °F, i.e., below freezing. As a result, frost injury was minimal, causing only burning of leaf margins (Figure 1).   

Table 1. Ohio regional minimum temperatures (°F) from 25 April and 27 April. Weather data from CFAES Weather System and NEWA

Weather Station

25 April min temps (°F)

27 April min temps (°F)

Ashtabula (Northeast)



Avon Lake (North Central)



Caldwell (Southeast)



Cincinnati (Southwest)



Columbus (Central)



Fremont (Northwest)



Piketon (Southcentral)



Wooster (Northeast)




Figure 1. Leaf margins burned after a frost event, bus the shoot is still alive (photo by Dami).

Factors affecting frost injury:

Phenological (developmental) stage: During deacclimation (March-April), grapevines become increasingly sensitive to temperature below freezing (32 oF) and critical temperatures (CT) vary with the stage of bud development. That is, buds become more sensitive as they grow in early spring. CT of buds or young shoots is defined as the air temperature that causes 50% damage after exposure for 30 minutes. The following is an example of CT of Pinot noir at different stages of bud/shoot development:

Stage of development

Critical Temperature (CT)




Dormant bud



Swollen bud stage



Bud burst (break)



First unfolded leaf



Second unfolded leaf



Fourth unfolded leaf



Weather conditions: CT also varies with weather conditions including air relative humidity and corresponding dew point. Dew point (DP) is the temperature at which water condenses out of the air as dew or the temperature that corresponds to 100% relative humidity.  Condensation releases heat and slows the drop of air temperature. Thus, if DP is higher than CT, heat will be released before reaching damaging temperatures and may provide some protection.  If the air is dry, DP is low and temperature will drop rapidly and may reach CT and thus cause more damage. 

Early budding varieties are also more susceptible to spring frost. For example, Marquette, La Crescent, Concord, Chardonnay break buds early in Ohio and thus tend to be sensitive to spring frost. Late budding varieties such as Vidal rarely sustain frost damage. Further, varieties bear fruit on shoots originated from primary buds. Some bear fruit from secondary and base buds. Secondary and base buds of Vinifera and Native grapes are not as fruitful and thus may sustain more crop loss than Hybrids. Secondary buds may produce 30-50% of the crop potential. Tertiary buds typically are not fruitful regardless of variety.

Figure 2. Frosted shoot and new shoot emergence from spur base bud (Archive photo by Dami)

What to do after a frost event?

  • First, do not give up! Grapevines have an amazing way of recovering and compensating for yield. Also, the percent of damage does not equate the percent of crop loss.
  • Whether the damage is severe or not, you should not discontinue your disease and insect management program. You need to keep the vine canopy healthy.
  •  Fertilization: if the damage is severe and only fruitless shoots recovered, this situation may lead to excessive shoot growth and vigor. You should avoid nitrogen fertilization. If the damage is minimum and a normal crop is expected, continue a normal fertilizer program. If you practice split application of nitrogen (N), skip the first one and then, based on the fruit to shoot growth, decide whether to apply the post-fruit set N application. 
  • Canopy management: due to excessive foliage and resulting shading you may need to be more aggressive with your canopy management practices. This practice will vary with the level of frost damage and variety. Like any other vineyard operation, it comes down to practice cost and the “well-being” of the grapevine. Sometime, the two factors do not go together. It is up to the grower to decide which way to proceed. Since there are many scenarios to consider that are dependent on the type of frost damage (partial or complete) and variety.
  • Provided below are two specific examples of canopy management based on reported research in Indiana and California.
    1. Our colleague, Dr. Bruce Bordelon at Purdue University, conducted a trial to manage several hybrids after a frost event that caused partial frost damage. Damaged shoots were either pruned (shoot or spur) or left intact (untreated control). With Marquette, pruning damaged shoots resulted in increased yield and better cane quality (size) the following year.
    2. Glenn McGourty, past OGWC speaker and viticulturist at UC Davis, conducted a similar trial with Chardonnay. He also found that removal of damaged shoots resulted in higher yield. Fruit ripening was delayed, but fruit quality was unaffected. In both situations, there was added labor to remove damaged shoots (20 to 30 hrs/acre). However, the extra cost in the year of frost damage was justified with less labor for pruning the following season and better cane quality. Basically, a severe frost year was a good year to “clean up” old cordons for new spur development. If you have a specific situation and undecided how to proceed, please do not hesitate to contact me.   
  • Disaster Assistance: Contact your local USDA-FSA (Farm Service Agency) and report your crop loss. It is important that you record the extent of damage you have, in case some assistance program becomes available.



May 1, 2023 - 2:47pm --