Adaptive Viticulture Strategies to Enhance Resilience and Grape Quality in Cold Climate Regions in Response to Climate Warming

Abstract

Cold climate viticulture is challenged by climatic variability, including increased frost risk, shorter growing seasons, and unpredictable weather events that impact vine productivity and grape quality. Global warming is altering traditional viticulture zones, prompting the exploration of new regions for grape cultivation, the selection of climate-resilient cultivars, and the implementation of adaptive practices. This review synthesizes recent advances in adaptive viticulture practices and plant growth regulator applications, highlighting novel molecular and physiological insights on cold stress resilience and berry quality. Key strategies include delayed winter pruning to mitigate frost damage, osmoprotectant application to improve freeze tolerance, and canopy management techniques (cluster thinning and defoliation) to enhance berry ripening and wine composition. Their effectiveness depends on vineyard microclimate, soil properties and variety-specific physiological response. Cover cropping is examined for its role in vine vigor regulation, improving soil microbial diversity, and water retention, though its effectiveness depends on soil type, participation patterns, and vineyard management practices. Recent transcriptomic and metabolomic studies have provided new regulatory mechanisms in cold stress adaptation, highlighting the regulatory roles of abscisic acid, brassinosteroids, ethylene, and salicylic acid in dormancy induction, oxidative stress response, and osmotic regulation. Reflective mulch technologies are currently examined for their ability to enhance light interception, modulating secondary metabolite accumulation, improving technological maturity (soluble solids, pH, and titratable acidity) and enhancing phenolic compounds content. The effectiveness of these strategies remains highly site-specific, influenced by variety selection and pruning methods particularly due to their differences on sugar accumulation and berry weight. Future research should prioritize long-term vineyard trials to refine these adaptive strategies, integrate genetic and transcriptomic insights into breeding programs to improve cold hardiness, and develop precision viticulture tools tailored to cold climate vineyard management.

1. Introduction

Global warming has significantly affected viticulture, altering grapevine distribution, phenology, and physiological processes across traditional wine growing regions [1]. Rising temperatures have accelerated heat unit accumulation [2,3], leading to earlier harvest dates, and producing high-alcoholic wines with high pH [4]. Over the past decades, bioclimatic indices have shown a significant warming trend [5,6], with regions such as Neuchatel experiencing a 0.56 °C increase in the growing season temperature per decade and a shift from a very cool to a temperate climate. As a result, many traditional viticulture valleys become less suitable for cold-adapted varieties like Pinot noir, while favoring more thermophilic varieties such as Merlot [6]. Vineyards are expanding into cooler regions, including higher latitudes and elevations, where water availability, temperature variability, and the need for site-specific adaptation strategies present new challenges [7]. Cold climate viticulture zones remain in a state of climatic transition, experiencing significant variability in temperature and seasonal patterns [1]. Over the past three decades in the Cautín Valley of Southern Chile, high temperatures and spring frost risk damage have significantly increased [1]. Although these conditions may enhance berry ripening, they also increase climate-related risks, threatening vineyard sustainability in these areas. On the other hand, a study identified two key challenges for winemaking in the Italian Alps: (1) cool-climate conditions are shifting to higher elevations, affecting current vineyard areas, and (2) regions at lower elevations may lose traditional production zones, requiring adjustments to wine region boundaries [8]. Thus, understanding the climatic thresholds beyond which grapevine performance is compromised is essential for designing adaptation strategies in viticulture. Breeding programs targeting cold climate resilience, such as those developing cold-hardy and disease-resistant cultivars, play a key role in this process [9].

Cold climate viticulture is practiced above the 42° parallel in the Northern Hemisphere and below the 37° parallel in the Southern Hemisphere, where growing seasons are short and heat accumulation is limited. In these regions, the mean growing temperatures range from 13 to 15 °C [10]. Under these agroecological conditions, berry development is fast, while the ripening is highly dependent on the post veraison climate conditions [11]. Moreover, insufficient heat accumulation during critical phenological stages, such as flowering, can significantly reduce yields [12]. An optimal scion–rootstock combination can promote earlier acclimation in the fall, enhancing cold hardiness during autumn and winter, while delaying deacclimation in spring to reduce the risk of damage from late spring frosts [13]. Thus, the selection of cold-tolerant varieties and the implementation of specific viticulture practices are crucial to mitigate the frost risk, control disease pressure, and optimize sunlight exposure and air circulation for wine production.

One of the defining characteristics of cold climate viticulture is high precipitation levels (>1000 mm annually) during the growing season, which can increase disease susceptibility and pest pressure [14,15]. Fungal diseases such as powdery and downy mildew, black rot, and gray mold, along with pests, necessitate frequent pesticide applications [16,17,18]. However, excessive pesticide use raises production costs, poses environmental risks, and may contribute to soil degradation and biodiversity loss [19,20]. Additionally, climate variability, including erratic rainfall and heatwaves, can have complex effects on vine growth, sometimes improving yield and berry composition but also intensifying climatic stressors [19,20]. Unpredictable spring frosts remain one of the most significant threats, often resulting in severe crop losses and requiring adaptive strategies [21]. While cold stress is the primary concern in these regions, episodic high summer temperatures also may occur, leading to accelerated ripening, sunburn, acidity loss, anthocyanin decrease, and altered aromatic profiles in some vintages [19,20]. Despite these challenges, cold climate viticulture offers unique opportunities. Grapes grown in these environments often exhibit higher amino acid content, lower sugar accumulation, and greater aromatic complexity compared to those from warmer regions [22].

Vineyard practices such as cluster thinning improve ripening uniformity and yield control [23], while cover cropping mitigates excessive vigor, improving soil structure and grape quality [24]. Given the increasing unpredictability of climate conditions, the development of adaptive viticulture strategies is crucial to maintain production stability and wine quality and typicity in cold regions [25]. This review synthesizes current research on viticulture practices that enhance resilience in cold climate vineyards, focusing on techniques such as delayed pruning, plant growth regulator applications, and alternative soil management approaches. By providing a comprehensive analysis of these strategies, this review aims to support viticulturists in implementing sustainable, evidence-based solutions to address the evolving challenges of cold climate viticulture under climate change.

2. Post-Budburst Pruning

Post-budburst pruning or late pruning is a viticulture practice designed to delay budbreak and subsequent phenological stages, thereby reducing the risk of spring frost damage. By postponing pruning until the “wool” bud stage (late winter), the budburst is naturally delayed, reducing the risk of frost injury during early spring [26]. Further delay in spur-pruning modifies vegetative growth, shifting flowering, fruit-set, ripening, ultimately influencing berry composition at harvest [27]. This technique is particularly valuable in regions where early budbreak varieties are highly susceptible to late spring frosts [26].

Pruning when apical shoots on cane reach 5 cm in length can increase yield by 93%, 6%, and 82% over three studied seasons of experimentation, primarily due to improved berry and cluster weights [28]. This could be due to better flower fertilization and seed development later in the season under more favorable climatic conditions. Additionally, in vineyards affected by spring freeze events that damage up to 33% of developing primary shoots, post-budburst pruning can promote secondary shoot development, partially compensating for yield losses. However, secondary shoots typically have lower fruitfulness, making their contribution to yield recovery variety-dependent [29]. However, delayed pruning does not consistently affect wine chemistry, carbohydrate storage, or bud freeze tolerance in subsequent dormant seasons.

Despite these benefits, delayed pruning can deplete carbohydrate reserves stored in the roots and trunks, which are critical for winter survival and early season vine growth [30]. This depletion may impair frost resilience in subsequent seasons, creating a trade-off between short-term yield gain and long-term vine health. Moreover, excessive winter pruning can lead to reductions in yield per vine and berry number per cluster, emphasizing the importance of precise timing [23]. The timing of pruning is crucial for maintaining vine vigor. Ideally, pruning should not extend beyond the two unfolded leaves stage, due to reductions in carbohydrate reserves and impaired early-season growth [23,27]. The phyllochron, defined as the thermal time between the sequential leaf emergences, serves as an indicator of carbon reserve depletion post-budburst [31]. Effective post-budburst pruning strategies should integrate vine carbon allocation from the previous season to optimize vine balance and resilience [27,31]. Late winter pruning (BBCH-12) and very late winter pruning (BBCH-17) delayed budburst by 17 and 31 days, respectively, compared to standard winter pruning (dormant buds) [23]. Late winter pruned vines exhibited greater canopy efficiency, reaching peak photosynthesis more quickly, achieving a 37% higher maximum carbon assimilation rate, and maintaining elevated activity from veraison to season’s end. Consequently, this treatment resulted in a 17% higher seasonal carbon accumulation than standard winter pruning, highlighting its potential to enhance vine performance and resilience under changing climatic conditions.

The effectiveness of this technique can vary significantly across different grape varieties and vineyard conditions. Grape varieties exhibit inherent differences in their budbreak periods [14]. Delayed pruning can be particularly beneficial for early budburst varieties by postponing this phenological event to a safer period. Since this practice is effective for frost risk mitigation, its feasibility depends on vineyard labor and management logistics. Delayed pruning requires additional labor input, particularly when applied at scale, as viticulturists should return multiple times to prune different sections at the appropriate phenological stage. Furthermore, the effectiveness of late pruning varies by grape variety and vineyard conditions, with some cultivars responding more favorably to delayed budbreak than others. Site-specific studies are necessary to refine pruning recommendations for different terroirs and management systems.

Post-budburst pruning is a valuable tool for managing frost risk in cold climate viticulture. However, improper timing, especially when performed too late, can deplete carbohydrate reserves, reduce vine vigor and increase vulnerability to frost in subsequent growing cycles. To maximize benefits and minimize drawbacks, viticulturists should balance yield optimization with long-term vine health, integrating carbohydrate storage dynamics, varietal response, and economic feasibility into their pruning strategies.

3. Osmoprotectants

Osmoprotectants, also known as cryoprotectants, are small organic molecules that stabilize proteins and cellular structures, aiding organisms in withstanding osmotic stress [32,33]. These compounds have been studied for their potential to enhance grapevine resilience against spring frost damage [34]. Early research in the 1990s demonstrated that applying cryoprotectant chemicals reduced the low temperature exotherm in grape buds, suggesting an enhancement in freeze resistance [35]. More recent formulations have been tested across cold climate viticulture regions to improve grapevine frost tolerance [36].

A potassium salt-based fertilizer with potential cryoprotectant activity was evaluated in different grapevine varieties cultivated in Pennsylvania. When applied 24 h before freezing conditions, this treatment reduced shoot mortality by 16% and lowered osmotic potential (–0.92 MPa) compared to untreated cuttings. However, researchers noted that while such treatments provide some level of protection, variety selection remains the most reliable strategy for mitigating spring frost damage [37]. Similarly, antifreeze agents composed of plant growth regulators, microorganisms, macroelements, and enzymes were tested in Chardonnay and Cabernet Sauvignon to prevent low-temperature stress [36]. These treatments significantly reduced relative conductivity and malondialdehyde content in tender shoots, enhanced osmotic adjustment and antioxidant enzyme activity, and increased the Fv/Fm ratio, indicating improved photosynthetic efficiency [36]. Optimal timing for applications of osmoprotectants is crucial and should consider vine development stage [32]. Application 24 h prior to frost exposure yields better results than when it is applied 48 h prior, and this enhanced berry soluble solid content, anthocyanin, total phenol, tannin, and flavonoid and flavonol accumulation in the berry skin [36].

Among natural osmoprotectants, glycine betaine has been studied for its role in enhancing frost tolerance in grapevines [34]. This compound stabilizes cellular structures and mitigates osmotic stress during freezing, promoting grapevine resilience [34]. In Chardonnay and Pinot noir clones, glycine betaine increased the number of days to reach maximum leaf area and improved specific leaf weight, without adversely affecting leaf water potential or physiological parameters [34]. In table grape varieties, it enhanced frost tolerance by up to 3.07 °C during the deacclimation stage for the Michele Palieri variety, and by 1.75 °C for the Red Globe variety [38]. These results can be highly significant in commercial vineyards, particularly during late spring frost events, where even 1–2 °C can determine the difference between full crop survival and severe bud loss. The findings underscore the plasticity of cold hardiness, which varies with genotype and is strongly influenced by temperature, with acclimation occurring in autumn and early winter and deacclimation in late winter and early spring [39]. As cold hardiness is a critical factor in plant survival in cold regions [40], integrating cryoprotectants into viticulture strategies may help maintain yield stability in frost-prone areas [39,41,42].

Despite promising experimental results, the practical application of osmoprotectants in viticulture remains complex. Some factors such as optimal timing, concentration, and potential impacts on grape quality, including vintage and varietal effects, should be carefully evaluated in future studies. Moreover, while some studies suggest that osmoprotectants can offer substantial protection against cold-induced damage, other reports have indicated that the response may be less pronounced in varieties that already hold endogenous stress response mechanisms [32]. Despite this, overaccumulation or dysregulation due to the application of osmoprotectants may interfere with primary metabolism, potentially affecting sugar concentration, berry size, or secondary metabolite profiles [32]. For example, in some crops, excessive osmolyte buildup has been associated with imbalances in carbon and nitrogen allocation, which could influence fruit development and quality parameters. Although direct evidence in grapevines remains limited, these findings highlight the need for careful optimization of the dosage and timing in future field applications. Furthermore, osmoprotectants should be considered part of an integrated frost protection strategy, complementing variety selection, canopy management, and post-budburst pruning to enhance overall vineyard resilience. Continued research is needed to refine these applications and ensure their economic viability and consistency across different viticulture environments. In this fashion, economic analyses specific to vineyards are scarce, and cost–benefit ratios likely depend on the application method, number of treatments per season, product cost, and the severity or frequency of stress events.

4. Cluster Thinning

Cluster thinning (CT) is a widely used technique to regulate crop load, improve ripening uniformity, berry composition, and wine sensory attributes, particularly in cool climate viticulture. Selective cluster thinning improves source–sink relationships, redirecting resources to fewer berries, and improving sugar accumulation, phenolics, and acidity balance. While CT generally reduces yield and improves berry composition, its impact is highly variable and strongly dependent on the compensatory ability of different varieties, thinning intensity and timing, and agroecological conditions. In Cabernet Franc, CT reduced the yield by up to 46%, but without impacting on cluster or berry weight or berry count [43], a similar result was reported for Chambourcin [44,45].

In Syrah, high-intensity thinning to one cluster per shoot at veraison led to the up-regulation of hexose transporter VvHT genes (VvHT2-3, 5, and 6) and enhanced sugar accumulation, anthocyanins, and tannins, alongside a decrease in titratable acidity and malic acid, indicating improved ripening [46]. Thinning also improved the grape composition of Cabernet Franc, without having a significant impact on TSS [37]. In Pinot noir, severe thinning led to a decrease in titratable acidity and an increase in pH [47]. In Chambourcin, severe CT (10 clusters per vine) led to an increase in TSS and pH, thus positively impacting berry composition [39].

A similar result was seen in Vidal Blanc [48] with limited impacts of thinning on titratable acidity [39,42]. In Riesling, severe thinning (1–1.5 clusters per shoot) significantly reduced the yield while improving TSS in two of three study years [49]. In Pinot noir, vigor-based differential thinning (2 or 1 cluster on strong and 1 or none on weak shoots), prior to veraison, enhanced varietal volatile compounds, including monoterpenes (linalool, geraniol, nerol) and C₁₃ norisoprenoids (β-damascenone, β-ionone), which contribute to floral and fruity aromas. This also increased the anthocyanins, polyphenols, color intensity, mouthfeel, body, and structure of the wines. Wines exhibited more rose and violet-like aromas (β-phenylethyl alcohol) while reducing green herbaceous notes (C6 alcohols, hexanoic acid), resulting in a more expressive and structured wines [47]. However, not all varieties respond favorably to CT. For instance, in the Probus variety (VIVC variety number 9719), thinning did not significantly enhance grape ripening or phenolic accumulation, highlighting the impact of varietal traits, such as natural vigor and sink strength, on the effectiveness of crop load adjustments [50]. These contradictions likely arise from differences in experimental design, vine vigor, and climatic conditions. A meta-analysis could help clarify these inconsistencies, providing a comprehensive understanding of the effectiveness of CT across various viticulture practices and regions.

When conducted four to eight weeks post-flowering or shortly before harvest, CT did not consistently improve phenolic berry composition or wine sensory quality of Pinot noir, despite reductions in yield [45,46]. Moreover, there was no effect of CT on growth, stored carbohydrates, and wine phenolics, despite a significant impact on berry phenolics in this variety being reported [51,52]. This suggests that a high crop load may be required for CT to produce a measurable effect, since Pinot noir vines in California’s Central Coast can sustain Ravaz Index values up to 6 without negatively impacting grape ripening [51,52]. In Grüner Veltliner, CT at bunch closure, combined with the defoliation of three basal leaves, significantly reduced yield but did not consistently improve berry composition, disease resistance, or winter hardiness [53]. Conversely, CT at the pea-size of berries has been shown to enhance anthocyanin biosynthesis, berry color, and wine quality in Cabernet Sauvignon [54]. However, when performed at same stage, Merlot did not consistently yield significant benefits across varying irrigation regimes or seasonal climates, indicating the strong buffer impact of external environmental factors on thinning [50]. Late thinning at veraison primarily influences sugar and anthocyanin synchronization, as demonstrated in Cabernet Franc, where it improved fruit composition without significantly increasing TSS at harvest [43]. This suggests that late thinning, at veraison, may be more effective than early CT in achieving uniform ripening and enhancing wine sensory characteristics, particularly in cool-climate viticulture. Additionally, late CT has been found to be most effective when combined with other techniques. In Cabernet Sauvignon, combining late CT with early leaf removal increased anthocyanin accumulation and improved color intensity, indicating that thinning strategies should be integrated with other vineyard interventions for maximum benefit [50]. This underscores the complexity of CT and the need for further research to determine its optimal timing, intensity, and interactions with other viticulture practices.

Despite its potential benefits on grape and wine quality, CT presents economic trade-offs due to yield reduction and labor-intensive implementation. In Riesling, lower crop loads led to significant reductions in economic returns, especially in years when price increases did not compensate for yield loss [49]. To compensate for those costs, bottle prices should be increased by $0.02 to $0.41 depending on the practice and vintage [55]. Additionally, the impact of CT on vine health and cold hardiness is uncertain, with excessive thinning in Grüner Veltliner leading to vine imbalances and reduced yield [53]. Furthermore, the necessity of CT varies based on seasonal climate conditions. In cool vintages, thinning can improve vine balance, sugar, and anthocyanin uniformity, enhance phenolic accumulation, and promote ripening for up to 10 days, making it beneficial for grape quality [47,56]. Conversely, in warmer vintages, the benefits of CT tend to diminish, as vines naturally reach optimal ripeness without intervention [43]. Therefore, cluster thinning may not always be necessary in warmer years, particularly when vines are well-balanced. Future research is needed to define variety-specific CT thresholds, the interplay between CT and other viticulture practices, and the long-term impact of this technique on carbon allocation and vine longevity. CT remains a valuable tool for fine-tuning grape composition and wine quality, but its application should be site- and variety-specific (Figure 1), ensuring that the potential benefits outweigh economic and environmental constraints.

5. Leaf Removal

Leaf removal (LR) involves the strategic removal of leaves, primarily from the basal of the vine, to enhance sunlight exposure, improve air circulation, and regulate vine microclimate. When applied early in the growing season, LR typically reduces berry mass but does not significantly impact overall yield in terms of the clusters count per vine [57]. Severe defoliation has been shown to reduce plant water consumption, by lowering transpiration demand [58]. However, excessive leaf removal can severely limit photosynthesis, compromising sugar, carbohydrate, and metabolite production, which is particularly critical in cold climate viticulture. Over-defoliation may negatively affect berry size, weight, and chemical composition, highlighting the need for careful management to balance benefits with potential drawbacks [59]. The timing of leaf removal is a key factor in determining its effects on vine physiology, yield, and berry composition. Early defoliation (before flowering or at fruit set) has been shown to reduce canopy density, enhance sunlight exposure, and improve cluster aeration [54]. This leads to a decrease in grape pH and enhanced titratable acidity, although the acidity response may vary based on the specific timing of defoliation [60]. Moreover, pre-fruit set leaf removal increased the synthesis of phenolic compounds, particularly anthocyanins and flavonols, resulting in better color and tannin structure in both grapes and wine [61]. In contrast, performing basal leaf removal after fruit set is particularly effective in delaying berry ripening, leading to lower TSS at harvest [60]. This technique can be beneficial in warm regions where rapid sugar accumulation often compromises wine, as it allows for a longer growing season and better accumulation of secondary metabolites in grapes. Additionally, conducting LR after fruit set is associated with better synchronization between sugar accumulation and anthocyanin biosynthesis, favoring more balanced phenolic development [60].

Leaf removal also influences grape aroma composition and wine sensory properties by modifying the synthesis of volatile compounds through sunlight exposure adjustment [62]. However, the varietal response to LR varies significantly. In Marselan, LR did not negatively impact aromatic compound synthesis, whereas in Cabernet Sauvignon early LR resulted in a decrease in norisoprenoid compounds, which are the key contributors to wine aroma complexity [62]. This is probably due to a higher tolerance of Marselana to leaf defoliation without compromising aroma profiles. However, specific experimental conditions, such as timing and severity of leaf removal, as well as agroecological conditions, play a crucial role in determining the outcome of LR. Recent studies suggest that early LR increases anthocyanins and flavonol concentrations in the initial stages of berry development, but these levels often normalize by the end of the season when compared to non-defoliated vines [61]. Leaf removal has been shown to enhance anthocyanin polymerization, contributing to wine color stability and longevity [61]. Beyond its effect on berry composition, basal leaf removal significantly reduces fungal disease by improving ventilation and reducing humidity around the clusters [63]. This is particularly important in humid regions, where fungal pathogens such as powdery mildew and botrytis pose major threats to yield and berry quality [63]. By improving airflow, LR (Figure 2) minimizes moisture retention on berries, reducing the need for fungicide treatments, and promoting more sustainable vineyard management. However, excessive leaf removal can lead to overexposure of grape clusters to sunlight, increasing the risk of sunburn and degradation of photosynthetic pigments and anthocyanins [64]. Moreover, the sunburn damage was higher when defoliation was performed late, at veraison [64]. The effectiveness of LR in vines can be influenced by its interaction with other vineyard practices such as canopy management, irrigation regime, pruning strategies, row orientation, and crop load control. Defoliation timing and severity interact with irrigation levels, where early leaf removal under water-limited conditions reduced berry size and yield but increased phenolic concentration [65]. In addition, in vertically shoot-positioned (VSP) systems, excessive defoliation can exacerbate sunburn risk and reduce photosynthetic capacity if not balanced with shoot thinning or lateral management [66]. The interaction with pruning strategy is also critical since late pruning delays phenology and modifies the canopy microclimate, which may require adjusting LR timing to avoid the overexposure of developing clusters [43]. These findings highlight that LR cannot be considered under high radiation zones, but rather as a component of an integrated vineyard management approach tailored to cultivar, site, and seasonal conditions.

6. Cover Crops

Excessive vine vigor in cool and humid climates increases canopy management costs, disease susceptibility, and compromises grape quality. Conventional bare-soil management, while reducing competition, often leads to soil erosion, nutrition depletion, and reduced microbial diversity. Integrating cover crops (CC) into vineyards is an efficient strategy for regulating vine vigor, improving soil health, reducing herbicide use, and promoting sustainable viticulture in cool-climate regions [67,68,69].

When compared to herbicide-treated strips, CC reduced vine pruning weight by 26% and increased berry exposure by 35%, leading to improved vine structure and enhanced ripening in Cabernet Sauvignon [67]. Among the cool-season perennial grasses evaluated as full vineyard floor cover crops, Elite II tall fescue (Festuca ovina L.) proved the most effective under high-rainfall conditions, reducing pruning weights by 28%, individual cane weight by 20%, and canopy leaf layer number by 25% in Cabernet Sauvignon, while maintaining a minimal impact on yield [70]. With moderate biomass and optimal stand density, Elite II tall fescue provided effective ground cover without excessive competition, outperforming KY-31 tall fescue, which produced excessive biomass and was less effective in vine vigor control [70].

The effectiveness of CC varies based on vineyard conditions and management practices. A three-year study in a Cabernet Franc in Ovid, NY, found that CC species impact vigor control differentially, with chicory reducing pruning weight by 64%, followed by tall fescue by 54% [68]. Both species suppressed shoot extension and reduced leaf density in the cluster zone, without yield reduction or affecting enological harvest parameters such as TSS, total acidity, pH, and yeast assimilable nitrogen (YAN) [68]. Previously, an enhancement of grape ripening and TSS was reported due to reduced vine vigor and due to an increase in cluster exposure flux by 42% and leaf exposure flux availability by 15% [67]. However, in a 20-year-old Riesling vineyard, CC holding buckwheat (Fagopyrum esculentum) and annual ryegrass (Lolium multiflorum) had no significant effect on vine growth, yield, petiole nutrient concentrations, stem water potential, soil organic matter, or juice composition when used in 1 m wide strips [71]. This suggests that mature vines can adapt to CC competition by shifting root distribution deeper, reducing total absorptive root length by 63%, yet maintaining canopy growth with minimal impact on water and nitrogen uptake [72]. CC-mediated changes in soil nutrient dynamics can impact on the wine aroma profile [71], underscoring the need for site and variety-specific CC management strategies.

CC can significantly affect vine nutrient uptake, particularly nitrogen and phosphorus. Reduced vine nitrogen content [73] negatively affects YAN levels, a critical factor in fermentation kinetics and wine aroma development [64,74]. Creeping red fescue (Festuca rubra), an under-vine cover crop, significantly reduced petiole nitrogen concentrations at bloom and veraison, negatively impacting fruit set and overall vine vigor in Cabernet Sauvignon [67]. However, a three-year study found that chicory, tall fescue, tillage radish, and alfalfa, along with natural vegetation, did not significantly reduce petiole nitrogen, though chicory lowered YAN for two years, compared to glyphosate-treated bare soil [68]. While leguminous CC can improve vine nitrogen status, their nitrogen release is not immediate, potentially leading to temporary nitrogen depletion before full biological nitrogen fixation is achieved [75]. Additionally, white clover (Trifolium repens L.) may contribute to increased nitrogen leaching in early spring due to its rapid tissue decomposition, highlighting the importance of species selection and strategic timing of cultivation and tillage [76]. Nitrogen supplementation may be needed to prevent excessive vine suppression and maintain optimal yields [67,77]. Long-term CC use has also been associated with a 34% reduction in petiole phosphorous concentration and a 17% decrease in fruit yield [72]. Despite these limitations, vines prioritize aboveground biomass production, allocating less than 1% of total biomass to fine roots, which may increase nutrient limitations and cold stress vulnerability, but also aid in vigor regulation and grape quality improvement in cold climate viticulture [72]. Effective supplementary phosphorus management, targeted cover crop selection, and strategic vineyard floor practices are crucial for mitigating potential drawbacks while maximizing the benefits of CC-managed vineyards. Beyond canopy regulation, CC contribute to disease and pest suppression. By reducing humidity and improving ventilation, CC minimize conditions favorable for fungal pathogens such as Botrytis cinerea and Uncinula necator. Additionally, CC increase populations of beneficial arthropods, reducing the incidence of pest species such as cyclodidae and mites [78].

CC reduce nutrient and pesticide leaching and improve long-term soil health in vineyards [76]. Studies in the Finger Lakes region demonstrated that chicory increased soil aggregate stability, microbial respiration, and carbon mineralization, which is critical for vineyards where nutrient cycling is slow [78]. Optimizing CC selection based on species-specific root architecture and competition for soil resources is critical. Annual CC, due to their short growth cycle and shallower root systems, exert less competitive pressure than perennial CC, making them more suitable for vineyards with low vigor. Moreover, integrating organic amendments such as wood ash, mussel sediment or municipal solid food waste with CC has been shown to improve vineyard productivity and grape sugar accumulation, particularly when combined with timothy-based CC [79].

CC represent a sustainable alternative to bare-soil vineyard management, offering multiple agronomic and environmental benefits in cool-climate viticulture. However, their economic feasibility must be carefully considered. The potential yield reductions due to nutrient competition must be weighed against long-term improvement in soil health, reduced input costs, and enhanced grape quality. The use of CC requires strategic management, including supplementary nutrient applications when necessary, to ensure vineyard productivity. The CC’s implementation must be adapted to vineyard-specific conditions, considering vine age, variety, soil type, and climate variability. The balance between vigor suppression, nutrient management, and yield stability remains a critical factor in optimizing the benefits of CC while mitigating potential drawbacks.

7. Light Film Technologies

Reflective ground covers, such as aluminum-based materials and photosensitive coated plastic films, have been studied for their potential to enhance grape quality in viticulture, particularly in cold climate regions [80,81]. These covers are applied to the vineyard floor to reflect sunlight onto the clusters, influencing grape composition [80]. For instance, the use of reflective film can double the reflected light under the vine canopy, leading to a 24.9% increase in net leaf photosynthetic rate [82].

A red geotextile reflective mulch applied from veraison to harvest in Riesling Italico, Traminer, and Manzoni Bianco in Zagreb, did not affect the TSS and titratable acidity of grapes, but increased the total phenol and flavan-3-ol content in wines of all varieties across different seasons [81]. Sunlight-reflecting film on the ground applied to Kyoho grapevines in Fujian enhanced firmness and skin anthocyanins, though it did not alter TSS in the berries [83]. Black geotextile inter-row mulch increased the air and soil temperatures, increasing soluble solids and reducing sugars in grapes [84]. Polypropylene aluminized mulch sheets placed beneath Riesling in Ontario increased free and bound terpenes in berries, while preserving acidity in the resulting wines [85]. Reflective mulch composed of aluminum platelets protected by a transparent film, sewn together with red polypropylene threads, increased epicatechin and gallic acid content in Merlot, Teran, and Plavac Mali grapevines [86].

The type of reflective ground cover material used can significantly influence the physiological and compositional outcomes in grapevines, including soluble solids accumulation [85]. These ground covers differ in their material composition, color, reflectivity, thermal properties, and light diffusion capabilities, all of which affect how light and heat are redistributed in the canopy and around grape clusters. For example, aluminized or silver-coated films tend to reflect a broad spectrum of light, particularly in the PAR and UV-A/B ranges, which enhanced both leaf photosynthetic activity and cluster-zone temperature [85,87]. This can, depending on climatic conditions, lead to higher sugar accumulation due to improved photosynthesis and increased translocation of assimilates to the berries. Another factor to be considered is the timing of application of the reflective ground cover. In this fashion, a reflective ground cover installed in sweet cherries at 21 and 34 days before harvest differentially affected the antioxidant capacity of fruits and the incidence of browning pedicel at post-harvest [88].

Reflective ground cover technologies (Figure 3) have demonstrated potential in improving grape quality parameters, including anthocyanin content, their direct effect on increasing TSS and enhancing acidity, particularly under cold climate conditions, requires further investigation. Despite this, their large-scale implementation remains limited due to logistical, economic, and labor-related constraints. Their deployment in commercial vineyards is often restricted to high-value cultivars or specific rows, particularly in cool climates or shaded environments, where optimizing fruit exposure is critical. Future research should focus on optimizing application methods and timing to fully assess the practical benefits of reflective ground covers in enhancing grape composition and overall wine quality in cold climate viticulture.

8. Plant Growth Regulators

Plant growth regulators (PGRs) significantly influence grapevine growth, cold hardiness, and stress adaptation under cold climate conditions [89]. Transcriptomic analyses revealed key pathways regulating endodormancy and freezing tolerance, including ethylene signaling, carbohydrate metabolism, phenylpropanoid biosynthesis, and protein metabolism [90]. Ethylene-related genes are highly responsive to low temperatures, indicating a potential role in modulating freezing tolerance. Although ABA is a known regulator of cold stress responses [90], its associated genes showed limited activation. The exogenous application of ABA, a key hormone regulating water balance and stomatal closure, enhances bud freezing tolerance [91]. The synthetic ABA analog, tetralone-ABA, further improves cold hardiness, delays budbreak, and slows deacclimation, presenting a promising strategy for dormancy resilience [92]. Additionally, ABA enhances antioxidant enzyme activity, mitigates oxidative damage, and maintains photosynthetic efficiency and leaf gas exchange following cold stress [93]. The timing of the ABA application influences its efficacy; treatments at veraison and post-veraison in Pinot gris have been particularly effective [94]. Importantly, ABA-induced early senescence and dormancy contribute to increased freezing tolerance without compromising yield or berry composition [94].

Brassinosteroids (BRs), a group of polyhydroxylated phytosterols, regulate growth and development and enhance plant tolerance to cold. BRs interact with various signaling molecules and phytohormones, such as auxin, cytokinins, gibberellins, ABA, ethylene, jasmonates, salicylic acid, and strigolactones, thus forming complex signaling networks [95]. BRs regulate the expression of genes related to stress adaptation, primarily those involved in antioxidant defense and osmotic adjustment [96]. Exogenous application of BRs (0.01 mg/L 24-epibrassinolide) and ABA (20 mg/L) improved chlorophyll fluorescence parameters, regulated antioxidant systems, and mitigated cold-induced leaf wilting, photoinhibition, and oxidative damage in one-year-old hardwood cuttings of Cabernet Sauvignon under cold stress [97]. BRs treatment alone up-regulates calcium-binding proteins, while ABA treatment alone up-regulates xyloglucosyl transferase genes involved in cell wall modification, contributing to structural reinforcement under stress [97]. Both BRs and ABA up-regulate Ethylene Response Factor (ERF) transcription factors, which mediate stress-responsive gene expression, interact with hormone pathways, and modulate secondary metabolism [97]. ABA and BRs interactions suggest a synergistic role in cold stress adaptation, with ABA potentially enhancing BRs effectiveness through shared signaling pathways or complementary gene expression regulation. BRs treatment resulted in a more marked effect on gene transcription with 2968 differentially expressed genes (DEGs) compared to 1359 DEGs for ABA and control [97]. The crosstalk between BRs and ABA involves complex signaling interactions that modulate plant responses to cold stress, evident in the up-regulation of ERF transcription factors common to both treatments [97].

Chilling stress markedly increased ethylene levels in V. amurensis, a cold-tolerant wild Vitis species [98]. Two transcription factor families, APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) and WRKY, were consistently up-regulated during chilling stress, however, their expression was inhibited by aminoethoxyvinylglycine, an ethylene synthesis inhibitor [99]. Ethylene-regulated genes mediate solute transport, protein biosynthesis, phytohormone signaling, antioxidant defense, and carbohydrate metabolism [99]. The observed increase in ethylene, indole-3-acetic acid, and ABA, aligns with transcriptomic data, suggesting that ethylene may regulate ABA and IAA responses, forming an integrated hormonal network that underpins cold stress adaptation in grapevine leaves [99]. These findings provide new insights into the complex regulatory mechanisms of ethylene under low-temperature stress and open new opportunities for breeding cold-resilient grapevines [98,99].

Salicylic acid (SA) treatments (1–2 mM) enhanced cold tolerance in grape seedlings by increasing antioxidant enzyme activity, soluble sugars, proline, and chlorophyll content [100]. Moreover, SA treatments significantly regulate the expression of cold response genes CBF1, CBF2, and CBF3 and induce the tolerance of Vitis riparia × V. labrusca to chilling stress [100]. Foliar application of SA strengthens the antioxidant defense system of cells, reduces ROS and lipid peroxidation, and increases membrane stability under frost stress [100]. Furthermore, SA (0.1 mM) improves chlorophyll fluorescence indices at −3 °C [101]. Preharvest SA application (3 mM) enhances YAN, amino acid levels, and phenylalanine-derived volatiles and terpenoids in developing Chardonnay grapes [102]. The SA treatment at a concentration of 2 mM reduced water loss and the activity of pectin-degrading enzymes, improving firmness and extending the shelf life and quality of Cheonghyang under low-temperature storage [103].

The application of PGR in viticulture necessitates a careful techno-economic analysis. While PGR can enhance cold hardiness and improve grape quality, their cost-effectiveness depends on various factors, including application costs and potential yield improvements. The excessive use of PGR, like gibberellic acid, has been linked to post-harvest issues, suggesting that optimal dosing is crucial for economic viability. Additionally, the long-term effects and environmental impact of repeated PGR applications warrant further study. Therefore, integrating PGR into vineyard management should be approached with strategies that balance immediate benefits with long-term sustainability and economic returns. ABA, ethylene, and BRs each contribute uniquely to enhancing cold tolerance in grapevines. A comprehensive understanding of their individual and interactive effects, coupled through techno-economic analysis, is essential for optimizing their use in vineyard.

9. Conclusions

Cold climate viticulture requires precise adaptation strategies to mitigate environmental stressors and maintain sustainable grape production. This review highlights various adaptive approaches, including delayed pruning, osmoprotectant applications, cluster thinning, leaf removal, and the use of plant growth regulators, as essential tools to enhance vine resilience against frost damage. Advances in transcriptomics and metabolomics have provided new insights into the roles of abscisic acid, brassinosteroids, ethylene, and salicylic acid in dormancy regulation and cold tolerance, suggesting that targeted hormonal applications could enhance stress resilience. While cover crops contribute to soil health and vineyard sustainability, their competition for nutrients necessitates site-specific species selection and careful management to balance vine vigor regulation and yield stability. Both cover crops and reflective mulch technologies demonstrate the potential to improve vineyard microclimates by reducing soil erosion and optimizing grape composition. While these adaptive strategies show promise, their effectiveness is highly dependent on site-specific conditions, grapevine variety, and precise application timing. Future studies should focus on long-term vineyard trials, economic assessments, and precision viticulture techniques to refine these strategies, ensuring sustainability in cold climate viticulture. By implementing these science-based strategies tailored to vineyard-specific conditions, viticulturists can improve vineyard resilience, maintain wine quality, and ensure the long-term economic and environmental viability of viticulture in the face of climate change.