86 MASS. EXPERIMENT STATION BULLETIN 388 



The Influence of Various Clonal Rootstocks on Apple Varieties. (J. K. Shaw 

 and L. Southwick.) The new stock bed set last year made a good growth and 

 should yield several thousand rooted layers in 1942. Several new stocks from the 

 United States Department of Agriculture were added. No layers were taken 

 from this bed this year but the old bed yielded a crop of layers that were lined 

 out for budding. Layers from the more vigorous stocks can always be budded 

 the first season but the dwarfing stocks require good growing conditions if they are 

 to be suitable for budding in their first year. 



The cooperative clonal stock orchards are as reported last year. Some are 

 doing well and should contribute to our knowledge of the interrelations of these 

 stocks with our American varieties; others are failures. One orchard that did 

 very poorly for the first three years has improved greatly in the last two years. 

 It is on a shallow soil with a high water table in the spring. During the past 

 two years it has been cultivated with a crop of string beans. The reason for 

 marked improvement may be that aeration of the soil has improved conditions 

 for root activity. An additional cooperative orchard of over 1000 trees on these 

 clonal stocks will be planted next spring. 



AH the trees in our own five-year-old orchard continue to grow about alike. 

 They have been in cultivation and have borne few apples, yet they are now large 

 enough to bear a bushel or more each. The orchard will soon be seeded to grass 

 which should bring the trees into bearing promptly and show whether the trees 

 on the various stocks react differently. Two trees of Red Spy on the very 

 dwarfing Mailing IX, one with several apples, broke off, emphasizing the fact 

 that trees on this stock should have support. 



The Mcintosh orchard planted in 1928 grew better than last year. Comments 

 on the mulched areas are made in the report on the Mulching Project. As meas- 

 ured by trunk diameter, Mcintosh trees on Mailing Xll, XV, and XVI and on 

 their own roots are now larger than the trees on seedling roots; trees on Mailing 

 X and XIII are somewhat smaller; and trees on Mailing I, V, and VI considerably 

 smaller. Trees on Mailing IV are almost as large in trunk diameter and spread 

 of top as those on seedling roots but are not as tall, indicating that this is a promis- 

 ing stock for fruit growers who wish to avoid tall trees. 



The trees on various stocks in the 1939 orchard continue to grow about the 

 same; little indication of dwarfing effect of the stocks has yet appeared. A few 

 scattered trees bore apples. In midsummer leaf scorch and partial defoliation 

 appeared. The symptoms suggested magnesium deficiency and an analysis 

 of leaf samples supported this. The trees were given a liberal application of 

 potash (with nitrogen) in the spring of 1941 and it has been shewn that potash 

 applications bring out symptoms of magnesium shortage. The situation will be 

 studied further and steps taken to remedy it. 



The diameter of the bulge or swell at the point of union and that above and 

 below the union were measured in June. The diameter above the union always 

 averaged smallest. The swell was larger with the stocks known to be dwarfing, 

 and was influenced also by the scion variety. It is doubtful whether the size of 

 the swell is of much significance in the performance of the trees. This work will 

 be more full)- reported elsewhere. 



Lethal Incompatibilities between Clonal Stocks and Varieties of Apples. 



(J. K. Shaw and L. Southwick.) The above project is concerned with stock- 

 scion combinations that may be useful in orcharding. There have appeared some 

 combinations that fail sooner or later. We have been unable to make some 

 of the flowering crabs grow on some of these clonal stocks. Cases are known in 

 which comestible varieties fail. Deeming this situation worthy of study, a new 

 project has been started in an effort to learn the reason for such failures. 



