2025 Post-Veraison in Pennsylvania - September 30

Report #5, Samples taken the week of September 22, 2025

This is the fifth weekly report for the third season of Post-Veraison in Pennsylvania (PVIP), a grape maturation reporting system across Pennsylvania vineyards. Reports consist of weekly grape ripening updates from cultivars that are planted widely across Pennsylvania (PA) vineyards (as based on feedback documented within Cultivars in the Commonwealth). Henceforth, PVIP reports will review the ripening patterns of some, or all, of the following cultivars: Cabernet franc, Chambourcin, Chardonnay, Riesling, and Vidal blanc. Due to the time required for grape samples to be shipped, processed, and measured, weekly reports will reflect maturation from the previous week.

Participating stakeholders for the 2025 edition of PVIP manage vineyards in the following Pennsylvania counties: Chester, Erie, Fayette, Lehigh, and Snyder; thanks to these stakeholders for their participation and collaboration on this project. If you have a commercial vineyard in Pennsylvania, please let us know if you are interested in participating in a future edition of PVIP.

Note that these fruit samples are sent in from commercial vineyards; due to sampling methods and other factors, the samples may not necessarily represent the overall maturity of each cultivar across the entire block. These reports are meant to provide updates on general trends; some fluctuation from "anticipated ripening trends" in metabolites will be expected. Nonetheless, trends over time should give a good depiction of wine grape maturation across Pennsylvania. To date, Chardonnay has been harvested in Lehigh and Snyder Counties and Riesling has been harvested in Fayette County. Grape samples from the week of September 22 were not received from Erie.

Primary fruit composition: soluble solids (Brix), pH, and titratable acidity.

From a "chemistry/lab-based quantification" standpoint, Cabernet Franc samples from September 22 revealed that fruit was more mature in Fayette and Snyder Counties relative to Lehigh and Chester Counties (Figure 1). Compared to the previous weeks' samples, Brix levels increased most dramatically in Fayette County (+5.2), followed by Snyder and Lehigh Counties (+1.9 in both counties); Brix decreased in Chester County (-1.2). Juice pH was higher in Fayette County (3.42) and Snyder County (3.51) relative to Lehigh County (3.19) and Chester County (3.08). Relative to last week, pH increased by the greatest magnitude in Snyder County (+0.30) and Fayette County (+0.24), while pH decreased in Lehigh County (-0.03) and Chester County (-0.12). The lowest titratable acidity (TA) values were observed in Snyder County (4.95 g/L) and Fayette County (5.40 g/L), which are the two counties in which TA decreased relative to last week’s values. Titratable acidity modestly increased Lehigh and Chester Counties, where TA values increased by 0.75 g/L and 0.15 g/L, respectively.

Note - the three counties that participated/are participating in PVIP in 2024 and 2025 are Erie, Fayette, and Snyder Counties. Average fruit composition from these counties is used to compare last year’s and this year's editions of PVIP (except for this report, which averages across Fayette and Snyder Counties since grape samples were not received from Erie County). Relative to the fifth week's report from 2024 (samples collected during the week of September 23), last week's samples showed: greater average Brix (+4.0), higher average pH (+0.18), and lower average TA (-0.34 g/L). These differences suggest that, on average, Cabernet franc primary fruit composition in 2025 is now relatively more advanced compared to the same period in 2024. Note that this is the first report in which the current year's trends have changed from "behind relative to 2024" to now "advanced relative to 2025."

Based on primary fruit composition, Chambourcin was similarly mature in Chester, Fayette, and Snyder Counties (Table 1). Relative to samples from last week, Brix increased at all locations, with the most pronounced increase (+1.1) observed in Fayette County, and lesser increases observed in Chester County (+0.6) and Snyder County (+0.2). Chambourcin pH increased by 0.12 in Snyder County and marginally decreased in Fayette County and Chester County. Relative to last week's report, Chambourcin TA decreased in Snyder County (-1.95 g/L), remained unchanged in Chester County, and increased in Fayette County (+1.20 g/L). Chardonnay was harvested in both Lehigh and Snyder Counties. Though Brix values were similar between this report and last week’s report, the greater pH and lower TA suggested that Riesling maturity advanced in Chester County. While Vidal blanc pH values remained similar in Snyder County, Brix increased (+1.4) and TA decreased (-2.55 g/L) relative to last week's report; these trends suggest that Vidal is progressing towards maturity and harvest in Snyder County.

Total sugars

It's important to recognize that soluble solids (°Brix) only provide an estimate of ripeness, since they measure all dissolved compounds in the juice, not just sugars. Direct measurement of glucose and fructose gives a more accurate picture of fermentable sugar levels, which directly drive yeast activity during fermentation. Tracking total sugars, and the balance between glucose and fructose, provides a stronger tool for predicting fermentation performance and final wine style than relying on soluble solids alone.

Total sugar content (glucose and fructose) was measured in some cultivar samples across some counties during the weeks of August 25, September 1, September 8, and September 22 (data not shown). The total sugars across dates (averaged across only the cultivars measured during that time point – which wasn't the same across dates) tended to increase over time; average total sugar values were 119 mg/mL during the week of August 25, 180 mg/mL during the week of September 1, 204 mg/mL during the week of September 8, and 232 mg/mL during the week of September 22 (data not shown). Cabernet Franc total sugars followed similar trends to the average across the cultivars measured across time points, with average total sugar values increasing over time: 117 mg/mL during the week of August 25; 185 mg/mL during the week of September 1; 213 mg/mL) during the week of September 8; and 238 mg/mL during the week of September 22 (Figure 2).

Pennsylvania stakeholders have reported harvest for the following cultivars in the 2025 vintage: Albariño, Aromella, Cayuga White, Chancellor, Chardonel, Chardonnay, Gruner Veltliner, Marquette, Merlot, Pinot grigio, Pinot noir, Pinotage, Riesling, Sauvignon blanc, Seyval blanc, and Traminette. If you have harvest updates you wish to be included in this report, please email them to viticulture@psu.edu.

The data in this report is possible due to the funding and support of the Pennsylvania Wine Marketing and Research Program. The authors and collaborators are grateful for the support.