Growth and fruiting of a spur-type and a standard strain of 'Golden Delicious' on several rootstocks over eighteen years

'Goldspur' a spur-type, and 'Smoothee,' a standard strain, of 'Golden Delicious' apple were evaluated on several rootstocks/interstems for 18 years. The dwarfs included Malling 9 (M.9), M.26, M.9/Malling Merton 106 (MM.106), and M.9/MM.111; the semi-dwarfs were M.7, MM. 106, and MM.111. Five single-treeplots were used. In-row spacings were varied with anticipated tree vigor and ranged from 1.8 to 5.5 m; between-row spacing was constant at 6.1 m. Both 'Goldspur' and 'Smoothee' trees were larger in trunk cross-sectional area (TCA) and height on M.26 and M.9/MM.111 than on M.9 or M.9/MM.106. Tree size on the three semi-dwarf rootstocks was largely unaffected by rootstock. Overall, the most root suckers occurred on trees of both strains on M.9/MM.111 and M.7. Yield per tree for both strains tended to be greater on M.26 and M.9/MM.111 than on either M.9 or M.9/MM.106. Although not significantly different, per-tree yields tended to be higher on MM.111 than on M.1 or MM.106. Crop density, yield efficiency, and average fruit weight varied relatively little among the various scion/rootstock combinations.