Preplant Soaking Duration of ‘Bartlett’ Pear Grafted onto Quince ‘Eline’ Affects Tree Growth and Stress in First Year of Establishment

Quince ‘Eline’ (Cydonia oblonga L.) is a cold-hardy rootstock for pear (Pyrus communis L.) that could potentially be adopted by the U.S. pear industry if it can be shown to perform under conditions that have prevented prior quince rootstock adoption. These conditions include colder winters and hotter, drier summers than the European regions where quince ‘Eline’ is currently used. Preplant soaking, the practice of submerging bare-root tree roots in water to rehydrate them following cold storage, will potentially be a critical component of preventing transplant shock if pear orchards grafted to quince ‘Eline’ are to be established in hot or dry areas. This study tested five soaking treatments for ‘Bartlett’ pear grafted on quince ‘Eline’ with a ‘Beurre Hardy’ pear interstem, and measured multiple factors related to tree establishment success throughout the first growing season. The treatments included a 0 h control as well as 24, 48, 72, and 96 h soaking times. The tree weight decreased when not soaked and increased when soaked for 48 or 72 h. Tree health remained similar among the soaking treatments, with all trees surviving, though the health assessment was limited by the use of an ordinal scale. The growth varied, with the 24, 48, and 72 h treatments showing the greatest trunk cross-sectional area and leader length increase. Stomatal-conductance-to-water-vapor measurements, used as a proxy for tree water stress, showed that the 96 h treatment resulted in more highly stressed trees. Altogether, this study identifies the benefit of preplant soaking for ‘Bartlett’ grafted to quince ‘Eline’, and highlights the 24 to 72 h range as a best practice for establishment for U.S. pear growers.