2025 Year in Review

By: Maria Smith and Diane Kinney, HCS-OSU

THIS ARTICLE SUMMARIZES THE 2025 DORMANT AND GROWING SEASON CONDITIONS AND THEIR IMPACT ON GRAPE VARIETIES GROWN AT THE RESEARCH VINEYARD OF THE CFAES-WOOSTER CAMPUS

WEATHER: TEMPERATURE

We find ourselves in a much more typical weather pattern for 2025 with regards to average monthly temperature (Figure 1). Aside from a very warm January and March, (+10 F and +5 F above long-term average, respectively), temperatures were near the long-term average. A January 21-22 polar vortex (-8 F) caused minor injury (10-15%) primary bud loss. Following this event, the season ahead looked favorable as we avoided any additional injury from spring frost. The remainder of the growing season (1 April through 31 October) remained near the long-term 30-yr average. Once again, we enjoyed a long fall with a late killing frost occurring on 10 November. Vines were able to acclimate energy and nutrient storage for the 2025-2026 winter through 207 FFD (frost free days), which were similar to the 218 FFD in 2024.

Figure 1. Temperature departure from 30-year long-term average for 1-Jan to 31-Dec 2025.

GROWING DEGREE DAYS

Growing degree days (GDD; base 50 F) was consistently ahead of the long-term average from March through October (Figure 2). Month by month, GDD fluctuated near average, with both May and August being cool but June and July warm. Our total GDD for the end of October was equal to our 30-year average (2994) for the entire year.  We ended the year nearly 300 GDD units lower than 2024 with a total of 3001. 2024 was our 3rd warmest growing season in the past 10 years with 3281 GDD units.

Figure 2. Monthly GDD from 1-Jan to 31-Dec for 2025, 2024, and the 30-year long-term average

Figure 3. Cumulative GDD from 1-Jan to 31-Dec for 2025, 2024, and the 30-year long-term average

WEATHER: PRECIPITATION

2025 has been a year of two seasonal extremes regarding precipitation. Seven of those months were far below the long-term average rainfall, ranging from -0.35” to -2.64”. The remaining months had precipitation far in excess of the long-term average, reaching excesses of up to 1.27” each month. Not only was total precipitation higher, but the frequency of rain events was high. April and May recorded measurable rain for 13 and 17 days respectively, making for a very wet early growing season.

Cumulatively through July, we averaged out to be in line with our long-term average. However, August and September precipitation fell off the charts, creating late-season drought conditions. For example, August only recorded 0.65” total for the month, which is nearly 2.5” below the monthly average. This is the third consecutive year we have been well-below average rainfall, with 2025 being the least amount of cumulative rain during the growing season. By end of 2025, we are over 4” below the long-term average for cumulative precipitation (nearly identical to 2024). While excessive drought conditions negatively impact vine vegetative growth, overall, it greatly benefited fruit quality at harvest with low late-season disease pressure along with higher maturation values.

Figure 4. Annual cumulative GDD compared the 30-year long-term average from 2016 to 2025.

Figure 5. Annual cumulative precipitation compared to 30-year long-term average from 2016 to 2025.

Figure 6. Monthly precipitation deviation from 30-year long-term average.

VINEYARD NOTES

It wouldn’t be agriculture if we didn’t face some unusual obstacle, and 2025 didn’t disappoint. We were entering bud-break feeling good, having avoided a winter freeze and, later, a spring frost, only to have continuous daily rain. This is the primary conclusion we have for the uneven fruit set development experienced across the vineyard, most notably in early flowering varieties. This resulted in very poor yields across most varieties in Wooster. Therefore, for the second year in a row, when we should have been seeing beautiful fruit and abundant yields at harvest, we instead were left shaking our heads and sighing. This rain also wreaked havoc on early disease development (Phomopsis) which required continuous monitoring and short 7-day spray schedules.

• Diseases and insects: An early season Phomopsis infection period created difficult to control shoot, foliage, and fruit infections, especially in early ripening hybrid varieties. Bird pressure in the fall was extreme this year, even with timely net application prior to veraison, likely due to grapes acting as a high quality food source under fall drought conditions. Damage from yellow jackets also was notable, although did not lead to fruit rot development.
• Fruit quality: Missing or shot berries was normal this harvest season driven from both excessive early rain and rain-induced Phomopsis infections. Typically, sour rot is the leading challenge to fruit quality, and we did see some again this year but in lower incidence. We did observe ‘stuck’ fruit ripening during September when pH wasn’t ideal and TAs remained high. Fortunately, dry conditions allowed us to hang our fruit to reflect more desirable harvest parameters, but acids often still remained higher than expected.

  

Figure 7. Composite photo showing Phomopsis infection in vegetation (shoots, leaves) and fruit (berries, rachis) and fruit set for Verdelho (top, middle left), Cab franc (middle center), Frontenac blanc (middle right), and Itasca (bottom).