The hazelnut plant, though able to withstand water shortage, in case of water stress reacts by reducing its perspiration with adverse effects on the production and development of leaf foliage, decreasing photosynthesis by closing foliar stomata and limiting nutrients assimilation. Especially in the period going from June to August, this has an effect on production and yield when opening the fruits: a crucial aspect for protected designations of origin, thus a high qualitative standard of the harvested product is required. If the hazelnut plant has an adequate amount of water available between the flowering periods and the fruit embryo formation, good results are obtained on an organoleptic level, in terms of having constant quality over time.