Notching Increases Branching 

 on Apple Trees 



Duane W. Greene and Wesley R. Autio 



Department of Plant & Soil Sciences, University of Massachusetts 



Frequently, a young apple tree does not 

 produce enough scaffold branches or secondary 

 lateral branches to fill the volume of its canopy 

 adequately. Chemical treatments can stimu- 

 late branching in these circumstances. 

 Promalin™ or one of its components, 

 benzyladenine, can be used to increase lateral 

 branching. Use of chemicals has not been 

 adopted widely by the industry, however, be- 

 cause it is difficult to regulate the number of 

 lateral shoots produced, and frequently, the 

 lateral shoots that are produced are too short to 

 develop into satisfactory scaffold branches. 

 Additionally, the rates of Promalin required to 

 stimulate lateral branching can thin developing 

 fruit and inhibit flower bud formation. 



Cultural techniques also can increase 

 branching in young trees. Pruning into one- 

 year-old wood increases lateral branching; how- 

 ever, this type of pruning reduces the potential 

 fruiting surface, reduces flower bud formation, 

 and creates a cluster of branches near the cut 

 that have narrow, undesirable crotch angles, 

 limb spreading can stimulate lateral branch- 

 ing, but the numbers of branches produced are 

 very small. Leaf removal also increases branch- 

 ing, but to be effective, the youngest cupped 

 leaves surrounding the apical meristem must be 

 removed, and the lateral shoots that are pro- 

 duced by this method often are too short to be 

 useful. Bending terminal shoots to the horizon- 

 tal during the dormant season and then reposi- 

 tioning them later in the season is effective but 

 time-consuming. Also, bending is easy only in 

 certain situations, e.g., in trellis plantings 

 where there are wires for tying. 



Another cultural technique which stimu- 

 lates lateral shoot development is notching. 

 Notching is defined as removing a section ofbark 

 above a vegetative bud. Removing this bark 



prevents the flow of the growth-inhibiting hor- 

 mone auxin from the tip of a shoot or branch to 

 the notched bud. Under normal conditions, 

 auxins are produced in shoot tips and move 

 downward in stems preventing bud break and 

 growth of buds below. This process of inhibition 

 of lateral bud growth by vigorous shoots at the 



Figure 1. The notching process. Bark 

 should be removed down to the wood in a 1/ 

 16-inch band above the bud and extending 

 approximately one third of the way around 

 the branch. This figure was derived from 

 Oberhofer, H. 1990. Pruning the Slender 

 Spindle. 



Fruit Notes, Winter, 1992 



