Journal of Arboriculture 21(1): January 1995 33 EFFECTS OF DEFOLIATION AND ANTITRANSPIRANT TREATMENTS ON TRANSPLANT RESPONSE OF SCARLET OAK, GREEN ASH AND TURKISH HAZELNUT by J. Roger Harris and Nina L. Bassuk Abstract. Combinations of defoliation and Moisturin®, a film antitranspirant, were applied to recently transplanted Quercus coccinea (scarlet oak) trees in August and to Fraxinus pennsylvanica (green ash) and Corylus colurna (Turkish ha- zelnut) trees in the late summer and fall of 1992.For scarlet oak trees, survival was poorfor all treatments. Moisturin®treatments aided survival and spring shoot extension for green ash trees transplanted in late summer, but showed no effect on later dates. Defoliation was detrimental to survival of green ash trees at all transplanting dates. Root regeneration did not occur on transplanted green ash or Turkish hazelnut before spring bud break. In the past, it has been claimed that the primary cause of death of transplanted trees is water stress (8). Water stress can be indirectly imposed by failure of the much reduced root system to provide water to the rest of the tree (5,6) or directly imposed by improper handling, especially on trees moved in a bare-root condition (16). The above- ground symptoms of water stressed trees include scorched leaves, twig die back and lack of vigor (15). These symptoms, and the accompanying slow post-transplant growth, are known as mani- festations of transplant shock. Transplant shock often reduces shoot extension for several years after transplanting (14). Since growth processes are physiologically the most sensitive to drought (7), post-transplant root extension may be severely restricted by water stressattransplanting, curtailing establishment. Evaporative demands, and the resulting po- tential for water stress, increase as late spring and summer temperatures increase, leaves develop, and transpiration increases. However, these warmer temperatures and photosynthesizing leaves promote root growth (9). The capacity for plant establishment, if favorable water balance is maintained, may therefore be greater than when the plant is dormant. With this in mind, antitranspirants have often been applied in an attempt to prevent water stress (4,11). The blocking of stomates by antitranspirants, however, has been shown to curtail photosynthesis for extended periods (3). Antitranspirants, may therefore hinder the development of new roots by reducing the production of current photosynthates, which are important for new root growth (13). Data on transplant response of pruned, non- dormant broad leaved plants are limited, but removal of leaves at transplanting has been shown to decrease post-transplant water stress in some instances. For example, Randolph and Wiest (10) found that Ilex crenata was less water stressed when shoots were pruned at transplanting, and Castle (2) found that citrus trees were less water stressed with increasing amounts of shoot prun- ing at transplanting. The objective of this research was to test the hypothesis that transplant response of scarlet oak, green ash and Turkish hazelnut transplanted bare-root out of the traditional spring season, can be enhanced by partial defoliation or the use of an antitranspirant. Two experiments, summer trans- planting of scarlet oak, and fall transplanting of green ash and Turkish hazelnut were initiated. Materials and Methods Summer Transplanting of Scarlet Oak. Mois- ture conserving treatments were applied to scarlet oak trees on August 16, 1992. Five treatments were randomly applied to four replicates (20 total trees). Treatments were: 1) no leaf removal (full leaf), 2) every other leaf removed (50% of leaves