S13 - Session P3 - Can reduction of autumn ferti-irrigation increase hydrangea quality during cold storage without consequences on flower quality?

Authors: Lydie Huche-Thelier *, Hanaé ROMAN, Nathalie Brouard, Rebecca Fewou, Thomas Eveleens, Vincent Guerin, Nathalie Leduc

With global climatic warming, autumns in Anjou (49, France) are hotter and drier, so ferti-irrigation of container-grown hydrangea need to be extended later. Even if growers use a lower nitrogen formulation for this autumn ferti-irrigation, plants receive sufficient nitrogen to promote green growth, this causes a delay in leaf nutrient remobilization which normally leads to their senescence and fall. Furthermore, in case of rainy autumn, these nitrogen supplies increase the risks of nitrogen leaching. As at the end of October, company stores all hydrangea production in fridge (around 2°C for at least 2 months to allow vernalization and to avoid frost damage to flower buds) and the leaves, still green and turgid, become mold and fall in fridge, needing costly manual evacuation by blowing. One solution to solve these problems could be to promote leaf senescence by reducing irrigation and/or by stopping fertilization supplies earlier in autumn. During two successive years in September and October, we applied, different ferti-irrigation protocols (halving of water supplies, stopping fertilization). Experiments were carried on four hydrangeas cultivars representing a panel in terms of vigor. We measured consequences on plant morphological and physiological parameters during autumn and after fridge storage, as well as on plant quality at blooming. Our results will be presented and the benefits of this eco-friendly tool to favour leaf senescence will be discussed. Produced by the Common Laboratory MATCH associating the UMR IRHS (INRAE, University of Angers, l'institut Agro Agrocampus Ouest) and Hortensia France, with the support of the ANR (French National Research Agency).