Summer Solstice Vineyard Update – June 2026

By: Maria Smith, HCS-OSU

We’re halfway through the year 2026, and the rollercoaster ride has been a wild one. I have been curious for a while just how our vine phenology has been matching up with long-term changes to weather patterns, and I will put together a look at this soon. However, for the upcoming July 4^th holiday, let me put it in baseball metaphor: the weather swings taken by this year have sent the ball out of the park. 

Let’s take a quick glance at the weather over the first half of the growing season… 

Temperatures and Growing Degree Days (Wooster)

The following figures will summarize monthly average temperature, total monthly precipitation, and growing degree days (GDD; daily average temp – base 50F), which represent heat accumulation units that correspond with phenological development of plant growth cycles.

By far, the greatest deviation in temperatures and precipitation came during April, which saw an overall average temperature deviation of nearly +7F and 3.5” of rainfall greater than the 30-year averages (Figure 1). This was particularly notable for early April, which is what drove so much rapid, early budbreak development and widespread frost damage. For growing degree days, the 30-year average for monthly GDD accumulation is 146. April 2026 accumulated a whopping 259 (+113). In contrast, April 2025 saw 159 and April 2024, our prior notable season of early budbreak, 182. 

May and June snapped back and cooled down substantially compared with April, but by that point, the damage was done. 

Can this pattern be related to this year’s building El Niño year? Probably. El Niño conditions officially developed earlier this month, which tends to mean, for Ohio, to expect overall cooler, wetter summer conditions, and warmer, drier winter conditions. That isn’t to say that we can’t still have punctuation marks throughout the year (!), as I write this at the start of a “heat dome” today… 

What then do I anticipate for the rest of 2026? Idealistic, optimistic me says we can expect an extended fall that lends itself towards full maturation for the fruit that we do have in Ohio this season and a lovely yellowing descent into vine acclimation for this winter. Of course, I want to be balanced to the converse, which says we could be looking at managing late season fruit rots and a winter that is marked by temperature swings that cause more bud injury. But let’s set the cynicism aside for today. 

 
Figure 1. Weather conditions (precipitation, average temperature, and GDD) from April 1 - June 28, 2026 for Hort Unit 2 in Wooster, OH. Data from https://newa.cornell.edu 

Phenology

We have been moving at a good clip at Unit 2 this year, and we are currently on schedule to be approximately 1 week ahead of the 2025 growing season. Here is a look across several cultivars at Hort Unit 2 for budbreak and bloom: 

Table 1: Phenology (budbreak (BB) and bloom) of key cultivars at Hort Unit 2, Wooster, OH for 2026 and 2025. 

Bloom into fruit set: 

Grapes exhibit a “double sigmoidal” growth curve, with two distinct phases of berry growth, one following fruit set (rapid cell division) and one from veraison to harvest (rapid cell expansion). We are currently in the first phase, where we have gone from flower to pea-size berries over the course of the past two weeks (Figure 2). In contrast to the 2025 season, we had overall good bloom-time weather conditions with moderate temperatures and dry conditions, leading to much better fruit set. When we reach lag-phase in a few weeks, we will be conducting crop estimates to understand how much yield we can anticipate towards harvest. 

Figure 2. Chambourcin at pea-size on June 25, 2026 at Hort Unit 2, Wooster, OH.

Canopy Management

June is the peak of canopy management time, where we wrap up shoot thinning and move directly into shoot positioning, wire placement, and leaf removal (Figure 3). I’d like to take a moment to refresh a few points on leaf removal here: 

Figure 3. Diane Kinney conducting leaf removal in Chardonnay at Hort Unit 2, Wooster, OH. (For those noticing the weed growth, we do in fact have weeds, contact herbicides were applied folloiwng the completion of leaf removal last week)

Leaf removal is a promoted targeted practice in Ohio to optimize sunlight exposure into the fruit zone of the canopy – it does not universally apply for every cultivar nor every training system.

1. Why conduct leaf removal? It improves canopy airflow, spray penetration, and sunlight interception into the fruit zone. For the Eastern US broadly, it is a key practice for disease management. For cooler regions and seasons, it promotes increased berry phenolic development in skin (increased color, mouthfeel, and riper aromas) and improved fruit composition (more sugar, lower acid).  

2. Sun burn, especially under hot and high sun exposure conditions, is a major risk associated with leaf removal (Figure 4). Caution should be taken for weeks like this where, again, we’re under heat advisory conditions… Leaf removal is best performed under cooler, cloudier weather (maybe next week?)
3. Traditionally, leaf removal is performed as close to fruit set as possible. This again minimizes sun burn risk. However, it’s common for that timing to extend about a month past fruit set.  

4. How much canopy to expose? For red cultivars on Vertical Shoot Positioning, we typically will remove leaves on both sides of the canopy. For white cultivars or cultivars on High Wire Cordon, we may selectively remove only the leaves shaded side of the canopy (E or N sides)
   
   
   Figure 4. Berry sunburn on HWC Marquette grapes following leaf removal. June 25, 2026, Hort Unit 2, Wooster, OH

Other notable issues around the state

Two major problems have arisen in the past month that have left a major imprint on the 2026 growing season:

1. More auxinic herbicide drift injury. This year has been particularly bad given the short windows of dry weather for herbicide applicators. Applications have been coinciding with the slowdown in growth in May and early June that has caused major crop-loss events in several vineyards (Figure 5). Record keeping/documentation, on site weather data, and reporting are all key and timely when it comes to responding to herbicide drift injury. Timeliness is important, and complaints can be filed with ODA directly. 
   
   Figure 5. Significant 2,4-D herbicide injury pre-bloom in Vitis hybrid on May 29, 2026.

2. Vine collapse (Figure 6) occurs when vascular tissue has been compromised, and the vine cannot move resources (water, nutrients, sugar) to sustain active shoot growth. This damage to the vine’s vasculature can occur through abiotic (e.g., cold injury, weedwhackers, girdling) or biotic stressors (e.g., crown gall, trunk disease). 
   There has been a notable amount of trunk injury (cracking, splitting) from both winter extreme lows and spring freeze stress that has been causing vine collapse this year. These injury events also contribute significantly to crown gall and trunk infections that may take time to become notable problems. Vines tend to be resilient, and while certainly demoralizing, they can usually be retrained from new growth suckers that arise from the beneath the trunk damage. This, however, may be less true for older vines that do not readily sucker. We have experienced several instances at the Wooster Vineyard where vines could not sustain additional cumulative damage and warrant replacement.  
   
   
   Figure 6. Early season vine collapse in Cabernet Sauvignon following winter injury, June 8, 2026, Ashtabula County, OH. Note that vine retraining can be conducted from new suckers emerging from the base of the vine that was protected with soil hilling in the fall of 2025.