398 SCIENCE PROGRESS 



twigs. The removal of some of the buds from trained trees, 

 in order to help the development of those which are left, is 

 also, properly speaking, a form of pruning, though it is generally 

 known as disbudding. 



Cutting Back 



The cutting off of about one-half or two-thirds of each 

 branch of a young tree when it is transplanted from the 

 nursery to the plantation is very generally recognised as being 

 the proper practice, though it is often omitted by the amateur, 

 who dislikes seeing his tree curtailed and learns too late that 

 such parsimony is false economy. The proper functioning of a 

 tree depends on the correct balancing of root-action to leaf- 

 action ; the one supplies the tree with water and food-material 

 derived from the soil, whilst the other is the channel through 

 which carbon is absorbed from the air : but as was explained in 

 the previous article, in transplanting a tree the existing root- 

 system is destroyed and a new root-system gradually has to 

 be evolved : the balance between roots and branches can only 

 be restored by curtailing the branches so as to adapt them 

 to the injured roots. This is the rationale of cutting back on 

 planting. The result of omitting the operation is very apparent, 

 especially during the first season and is often very serious. 

 Instead of forming good healthy leaves and a fair amount of 

 new growth, the leaves have been found to show a deficiency 

 of some 25 per cent, in size, little or no new wood being 

 formed. Photographs of two apple trees which were similar 

 when planted eighteen months previously are shown in figs. 1 

 and 2 (the staff shown in the figures is divided into feet) ; these 

 give a fair idea of the results of the two forms of treatment. In 

 the case of plum trees, which commonly fruit precociously 

 after transplanting, if not cut back, the trees will often be so 

 exhausted as to be killed. 



Although good horticulturists never question the advisability 

 of cutting back on planting, there is a considerable diversity of 

 opinion as to when this operation should be performed, some 

 advising that it be done at the time of planting, others at the 

 time when growth is starting in the spring, others again 

 advocating that it be deferred till one year after planting. 

 A number of somewhat elaborate experiments have been made 

 on this subject and it has been found that the time at which 



