I . Scion/ r ootstock and interstem effects on growth and fruiting 

 of apple trees . William J. Lord 



New rootstocks and also virus-free clones of both rootstocks 

 and varieties became available during the 1970's. A surge of 

 interest also developed in interstem trees due to the high cost 

 of providing support for trees on M9 , and an interest in high 

 density plantings. Thus, our basic objective in this project is 

 to evaluate tree size, yield, production efficiency and fruit 

 quality of several varieties on various rootstocks and interstem/ 

 rootstock combinations. 



Unfortunately, our oldest rootstock and interstem trials are 

 only 5 years old, which is short when one considers the long life- 

 span of apple trees. Nevertheless, our data and observations to 

 date show that interstem trees, particularly with Empire as the 

 variety, are more time consuming to train than are trees on more 

 vigorous rootstocks such as M7 , It has been necessary to stake 

 many interstem trees to support the leaders and to eliminate tree 

 leaning. 



Suckering is profuse on interstem trees planted with the stem- 

 piece/rootstock union 2 inches above ground level, whereas it can 

 be minimized by deeper planting. 



The presence of burrknots on the M9 stempiece is readily 

 apparent when the stempiece rootstock union of interstem trees is 

 above ground. On many trees the burrknots are large and numerous 

 and their presence has caused the stempiece to become twisted and 

 distorted . 



In plantings established at the Horticultural Research Center 

 in 1976, Empire trees on M9/MM111, M9/0ttawa 11, and M9/Antonovka 

 are larger and have been more productive than Sturdeespur Delicious 

 on similar interstem/rootstock combinations. Trees on M26, which 

 in general are doing poorly in many commercial orchards, have per- 

 formed well to date, Rogers Mcintosh has had higher production 

 efficiency on M26 than on M7 or MM106. Rogers Mcintosh on M26, 

 M7 or MM106 began fruiting in 1978 (in the 3rd leaf) whereas the 

 first crop of Gardner Delicious on the same rootstocks was harvested 

 in 1980. 



A planting of Empire on M26, M27, M9 , M9/MM106, M27/MM106, 

 M9/^0^111 or M27/MM111 was established at the Atkins Orchards, 

 Belchertown, MA in 1976. After 5 growing seasons differences in 

 tree spread are still small, although the spread of trees on M9 

 and M27 is less than that of trees on M9/MM106, M27/MM106 and M26. 



