THE BEST UNDERSTOCKS FOR NEW ENGLAND ORCHARDS 



C. Lyman Calahan, Extension Horticulturist 

 University of Vermont 



Apple growers have clearly proven that they are yery much 

 interested in planting young apple trees on size controlling root- 

 stocks. EM VII has been planted more than all of the other size- 

 controlling stocks in this area, but with full knowledge that 

 there are some shortcomings with this stock. 



Now a very significant shift from EM VII to MM 106 is occur- 

 ring, mostly because there is some hope that Mcintosh will grow 

 better on this stock. Unfortunately, our experience with growing 

 this newer rootstock in a cool climate and shallow or poor soils is 

 far too limited, leaving us unable to offer meaningful advice to 

 those planting MM 106 rootstocks. 



At the University of Vermont Horticultural Research Center, 

 we do have a research project under way to evaluate new rootstocks, 

 but it may be several years before much meaningful data will be 

 available. We selected M-26, MM 104, MM 106 and M. robusta 5 as 

 understocks in an effort to run the entire spectrum of size control 

 vigor and hardiness. The Mailing stocks came directly from East 

 Mailing as stoolshoots. 



Mcintosh and Richared Delicious were used as 2 of the scion 

 varieties. A third scion, our own Vermont Spur Delicious, was used 

 to learn more about the growth response of a spur type on the least 

 vigorous and most vigorous stocks used in the experiment. In addi- 

 tion, the variety Mutsu was used, not because it shows much commer- 

 cial promise, but because it is a very vigorous triploid and is 

 suspected not to be completely winter hardy. 



Unfortunately, an experiment of this kind cannot be gotten 

 under way as quickly as we would desire. The trees were finally 

 orchard planted last spring after almost 4 years of "lead time" 

 had elapsed. (Preliminary work was begun in 1963, and the stocks 

 were planted as stoolshoots in the spring of 1965. They were 

 budded that fall and grown at Burlington and Ottawa during the sum- 

 mer of 1966.) Furthermore, it is entirely possible that by the 

 time this orchard is mature, and meaningful data can be obtained, 

 these rootstocks will have become a mere curiosity, passed over by 

 the development of more promising stocks. And even if better root- 

 stocks are not found by then, we may be caught a little short- 

 handed on 2 or 3 counts when it comes to good research findings to 

 help the grower plan his plantings in the years ahead. First, we 

 won't know for a long time how successfully we will be able to grow 

 Mcintosh and Delicious in the hedgerow system, on the more vigor- 

 ous stocks, by limiting tree size with control pruning. A good 

 economic comparison between such trees and one on dwarfing root- 

 stocks will require a lot of careful work. Secondly, we are rap- 

 idly going in the direction of accepting the spur-types in order 



