2025 Post-Veraison in Pennsylvania - September 16

Report #3: Samples taken the week of September 8, 2025

This is the third weekly report for the third season of Post-Veraison in Pennsylvania (PVIP), a grape maturation reporting system across Pennsylvania vineyards. Reports will 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. For example, the persistently higher (and often increasing) titratable acidity values are expected to be due to the abnormally relatively dry and cool weather that has been experienced over the last several weeks. It is possible that the dry weather is concentrating the acidity (via smaller berries) while the cool weather is resulting in less acid respiration than would be experienced if overnight temperatures were warmer. Nonetheless, trends over time should give a good depiction of grape maturation across Pennsylvania.

Samples from the week of September 8 revealed that Cabernet franc tended to be most mature in Snyder County, followed by Lehigh, Fayette, and Chester Counties, while maturity in Erie County remained comparatively delayed (Figure 1). Compared to the previous weeks' samples, Brix levels increased most dramatically in Lehigh County (+7.2) followed by Snyder County (+2.1); Brix modestly changed in other counties. Juice pH was greatest in Chester County, followed by Fayette and Lehigh Counties, Snyder County, and was lowest in Erie County. Relative to last week, pH increased by the greatest magnitude in Chester (+0.25) and Lehigh (+0.24) Counties, while less dramatic changes were observed in the other three counties. Relative to last week's report, titratable acidity (TA) decreased by a large magnitude (-7.95 g/L) in Snyder County; however, TA increased in all other counties.

Note - the three counties that participated in PVIP in both 2024 and 2025 are Erie, Fayette, and Snyder Counties. Average fruit composition from these counties are used to compare last year's and this year's editions of PVIP. Relative to the third week's report from 2024 (samples collected during the week of September 9), last week's samples showed: lower average Brix (-0.8), lower average pH (-0.25), and higher average TA (+0.98 g/L). These differences suggest that, on average, Cabernet franc maturity in 2025 currently remains slightly delayed compared to the same period in 2024. However, in Snyder County, all maturity metrics (Brix, pH, and TA) indicated more advanced fruit maturity in last week's samples compared to the third week of PVIP in 2024.

Chambourcin was generally more mature in Chester, Fayette, and Snyder Counties relative to Erie County (Table 1). Relative to samples from last week, Brix moderately changed in Fayette County but increased by a range of 0.9-1.6 in Erie, Chester, and Snyder Counties. While Chambourcin TA modestly dropped in Snyder, pH increased by a range of 0.08-0.11 in Erie, Fayette, and Chester Counties. Compared to last week's samples, TA decreased in Erie (-5.70 g/L) but increased in all other counties by a range of 2.10 to 6.90 g/L. Chardonnay Brix, pH, and TA were all lower in Snyder relative to Lehigh County. While Brix remained relatively stable in both counties relative to last week's report, pH and TA decreased (-0.20 and -2.25 g/L, respectively) in Snyder County, while they both increased in Lehigh County (+0.16 and +2.40 g/L, respectively). As demonstrated by the greatest Brix and lowest TA, Riesling maturity appeared more advanced in Fayette County relative to Erie and Chester Counties. While Brix was greater in Chester County than in Erie County, the TA values were lower in Erie County relative to Chester County. Despite a 2.4 Brix decrease in Vidal blanc in Snyder County relative to last week's samples, Vidal blanc maturity remained consistently advanced in Snyder, where Brix and pH were greater (+3.0 and +0.21, respectively), and TA was lower (-4.20 g/L), when compared to samples from Erie County.

Table 1. Fruit composition [soluble sugars (Brix), pH and titratable acidity (TA)] for Chambourcin, Chardonnay, Riesling, and Vidal blanc during the week of August 25 and September 1. Note: higher Brix and pH and lower TA are generally associated with more advanced maturity.

Pennsylvania stakeholders have already reported harvest for some cultivars in the 2025 vintage, including Albariño, Aromella, Cayuga White, Chancellor, Chardonel, Chardonnay, Gruner Veltliner, Marquette, Merlot, Pinot grigio, Pinot noir, Sauvignon blanc, and Seyval blanc. In some cases, cultivars were picked at relatively low Brix and pH and high acidity to produce sparkling or rose wines. 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.