Sax and Gowen: Productive and Unproductive Apple Trees 295 



AN UNDESIRABLE TYPE OF BEN DAVIS APPLE TREE 



In an orchard of 881 trees, there were 136 of this type, which has been called type 3. 



The 



average annual yield of these trees during a five year period was only 39 lbs. of fruit per tree, as 

 opposed to 191 lbs. for trees of type 1, and 113 lbs. for trees of type 2. The unproductive trees 

 are rather small, upright in habit, with slender branches and few spurs. (Fig. 3.) 



yield of trees is found. From this it 

 may be concluded that yield is, in 

 general, dependent on the size of the 

 tree and that dififerences in size of 

 trees of the same age are closely 

 associated with a rather definite type 

 of growth, 



THE CAUSE OF PRODUCTIVE AND UN- 

 PRODUCTIVE TYPES 



Consistently unproductive trees have 

 often been attributed to inherent 



differences resulting from bud muta- 

 tion. In other words certain varie- 

 ties are thought to contain high and 

 low yielding strains of trees. There are 

 however, a number of factors which 

 may cause consistent differences in the 

 productivity of trees in the same 

 orchard. The following are the im- 

 portant known factors: 1. Soil heter- 

 ogeneity, including such permanent 

 differences as soil moisture, depth of soil, 

 elevation, and physical and chemical 



