PRUNING 85 



general bulk pruning was treated, consisting in both head- 

 ing-back and thiiming-out of the young trees. The effects 

 of these two types of pruning on the branch growth and 

 the development of fruit-spurs may now be studied to 

 advantage. 



Heading-back refers to the cutting of the shoot or branch, 

 removing the terminal growing point and a certain number 

 of the lateral buds or shoots nearest the end of the branch. 



Thimiing-out, on the other hand, means the removal of 

 surplus branches or shoots without any heading-back proc- 

 ess. The effects of these two types of pruning are different 

 and should be carefully examined. 



The experiments of Gardner ^ in Oregon were so arranged 

 that the responses to these two types of pruning could be 

 studied in detail. They show in general that thinning-out 

 is more favorable to fruitfulness than heading-back, al- 

 though both practices would be included in orchard oper- 

 ations. The general response from the total or bulk pruning 

 was not entirely in accord with the experiments cited above, 

 in discussing the effect of pruning on size of tree, but varieties 

 varied to a considerable degree. With Grimes on Doucin 

 roots it made little difference whether a shoot was left un- 

 pruned or was headed-back lightly or severely, the subse- 

 quent units of growth the following season being about the 

 same. The number of shoots resulting if a branch was 

 severely headed-back would, however, be fewer than if 

 lightly headed-back or left unpruned. With the varieties 

 Esopus, Rome, and Gano, on the other hand, heavy pruning 

 checked their growth. These latter statements refer to the 

 effect of pruning on the subsequent size of the tree and are 

 not to be confused with those in regard to the development 

 of spurs and fruit-buds when trees are headed-back or 

 thimied-out. 



' Ore. Agr. Exp. Sta. Bull. 139. pp. 3-^5. 



