'Hedelfingen' sweet cherry fruit and tree growth responses to thinning and five rootstocks

Four dwarfing and one traditional, full-vigor, sweet cherry rootstocks; and several hand thinning vs. unthinned treatments were studied for their effects on horticultural characteristics of 'Hedelfingen' scion cultivar. Tree sizes, expressed in terms of TCSA (Trunk Cross Sectional Area), of 'Gisela 1' and 'Damil' were about 1/3 to 1/4 that of trees on 'Mazzard'. 'Gi 196/4' and 'Gisela 6' were about 1/2 of 'Mazzard', with 'Gi 196/4' being slightly bigger than 'Gisela 6'. Fruit diameter was also influenced by rootstocks. 'Mazzard' and 'Gi 196/4' had relatively large fruit size among rootstocks. Hand thinning increased fruit size when averaged across rootstocks. Its effect on fruit size depended on rootstocks. Semi-dwarfing rootstocks with high crop density responded well to thinning. The photosynthetic resource limitation began to be shown in the beginning of phase III of development because it was at this point that the difference in fruit size between the thinned and unthinned treatments was manifested.