Last Updated: 1/2025

Applies to:  Grape growers and winemakers subject to post-veraison heat and drought in their growing regions. This article details how these conditions can cause underripe characters and offers vineyard and winemaking mitigation tactics.

Drought conditions and heat waves are of increasing concern in many US growing regions, even in areas that don’t traditionally experience these weather events. Though hot and dry conditions can improve ripening and lower pyrazine levels, intense post-veraison heat and drought can have the opposite effect, leading to underripe characters. The hottest conditions can cause some of the slowest ripening and latest harvests. 

This is due to the fact that grapevine stomata begin to close around 95°F, and higher temperatures can damage the photosynthetic apparatus and impair fruit ripening. After multiple days of high heat, vines may take several days to recover, and some leaves may never recover due to irreversible damage (Keller, 2020). The vine essentially shuts down and ceases ripening during these conditions leading to slow flavor development and slow pyrazine degradation, while dehydration increases sugar and acid concentrations.

LALVIGNE® foliar sprays, in addition to canopy and irrigation management, can be a tactic for preventing unbalanced ripening. Used together, the LALVIGNE® foliar sprays work to prevent or limit underripeness caused by heat and drought stress, by improving vine adaptation to water stress (PROHYDRO) and stimulating the metabolic pathways that increase accumulation of phenolics (MATURE) and aromatic precursors (AROMA). At the same time, they also activate the secondary metabolism of the vine that is correlated with increased pyrazine degradation (MATURE and AROMA) (Suklje et al., 2016).

Scott Laboratories is excited to introduce LALVIGNE PROHYDRO™ to the U.S.! PROHYDRO naturally increases the tolerance of grapevines to water stress and is a blend of naturally ocurring amino acids derived from wine microorganisms that can be easily assimilated by grapevines. Applied preventatively, the selected blend of amino acids improves vine adaption to water deficits and increases vine recovery after periods of water stress. 

The ability to adapt to high water stress improves overall vine function, allowing for increased photosynthesis and transpiration. Ultimately, this helps combat underripeness by stimulating the vine’s primary metabolism (sugar accumulation and acid degradation). LALVIGNE PROYHDRO™ also works synergistically with LALVIGNE MATURE and AROMA to improve the vine’s secondary metabolism responsible for physiological/phenolic ripening.

LALVIGNE MATURE and LALVIGNE AROMA further stimulate the vine’s secondary metabolic pathways to increase accumulation of phenolic and aromatic precursors and degrade pyrazines. This combats underripeness and allows an earlier and larger harvest window.

Keller, M. (2020). The Science of Grapevines (Third Edition). Academic Press. https://doi.org/10.1016/B978-0-12-816365-8.09989-9
Šuklje, K., Antalick, G., Buica, A., Coetzee, Z. A., Brand, J., Schmidtke, L. M., & Vivier, M. A. (2016). Inactive dry yeast application on grapes modify Sauvignon Blanc wine aroma. Food Chemistry, 197, 1073–1084. https://doi.org/10.1016/j.foodchem.2015.11.105

For more information on making wine with underripe fruit including process and product recommendations, see our Best Practices for Working with Underripe Grapes.

Interested in setting up a trial with LALVIGNE? Reach out and get in touch to learn more.