8 MASS. EXPERIMENT STATION BULLETIN 422 



jnembered that the stimulation resulting from pruning is temporary. To be 

 maintained, it must be accompanied by fertilization of the soil. 



In the case of young trees, pruning is used to assist the tree to develop a strong 

 framework. Probably little can or need be done in this respect with young beach 

 plum bushes. 



The stimulating effect of pruning should be directed particularly at the por- 

 tions of the tree which form the fruit buds. The beach plum forms its fruit buds 

 on the current season's growth. Blooming and fruiting take place the following 

 year. Therefore, pruning should be directed at producing the maximum num- 

 ber of vigorous new shoots annually as described below. 



Beach plums are so variable in their growth habit that it is difficult to make 

 pruning recommendations which will fit all cases. In a broad general way the 

 bushes may be divided into two classes: (1) those which are low and spreading 

 and sprout freely from the roots, thus making a thicket-like growth; and (2) 

 those which have a tree-like form resembling cultivated plums in growth habit. 

 It would probably not be economic to use conventional pruning methods on the 

 first type of growth. Mowing with a brush scythe is certainly faster and, at least 

 from what is now known, is fairly satisfactory (Fig. 6 and 7). However, growth 

 following such treatment indicates that the stimulation is temporary. This 

 method of pruning has the disadvantage that one or perhaps two crops are lost 

 while the bushes are recovering. It is an established fact with other fruit plants 

 that, while they need some pruning, >ields are reduced in proportion to the in- 

 crease in severity,' of pruning. There is no reason to think the beach plum is an 

 exception. 



With the more tree-like forms, it will probabh' pay in the long run to prune 

 in the conventional way with shears and saw. First remove dead and weak 

 wood. Then remove all black knot cankers or other diseased wood, making the 

 cut several inches below the diseased portion. Finally, if the bushes are still 

 ^•ery thick, remove a few of the old branches to make room for young vigorous 

 growth. All prunings should be burned to destroy- diseased portions. 



Fertilization 



Because beach plums are general!}- found on ver\- poor soil, there has developed 

 the general impression that they will not respond to fertilizer treatment; that 

 they require a poor soil for their best development. If these notions are correct, 

 the beach plum is indeed an unusual fruit. Certainly no one would expect an\ 

 of the cultivated fruits to grow well and bear annual crops if they were continually 

 starved. That the beach plums are usually in a state of starvation is indicated 

 by the very small amount of growth that most bushes make. Also, the sandy 

 soil, in many cases almost pure sand, in which the\- grow is known to be very 

 deficient in all the chief fertilizer elements and may even be deficient in the trace 

 elements. 



To determine the effect of fertilizer, an experiment was started at Sandwich, 

 Massachusetts, in 1942. Three plots 27' x 35' were laid out. One plot was given 

 an application of 5-6-4 fertilizer on May 27 at the rate of 4000 pounds per acre. 

 The second plot was given the same formula and the same amount but split into 

 three applications, 100 pounds on May 27, 100 on June 10, and 200 on June 20. 

 The third plot was left unfertilized. 



Observations made on June 18, 1942, showed very little set on the unfertilized 

 plot, a fair set on the plot with split fertilizer applications, and a very good set 

 on the plot with a single application. This looks as if fertilizing beach plums 

 would be worth while. A severe drought during the summer caused all the small 



