instead of producing flower buds. This appears to explain why 

 the USDA trees were less productive than the tier trees in 1979. 



Trees with limbs in tiers . Trees pruned by this system responded 

 similarly to the USDA trees in regard to growth in 1976, 1977 

 and 1978 and to yield in 1978 (Table 2). However, these trees 

 were more productive than the USDA trees in 1979 and trunk cir- 

 cumference increase was less. Pruning time has been less because 

 no heading cuts were made on 1-year-old branches on scaffold 

 limbs . 



Slender spindle trees . Pruning of the slender spindle trees has 

 been the least time consuming of the 4 systems. The trees, based 

 on trunk circumference increase, produced more growth than the 

 heavily pruned USDA and tier trees in 1976 and 1977 and more fruit 

 in 1978 (Table 2). In 1979 yield on the slender spindle trees was 

 higher than on the USDA tree. 



It is well known that non-pruned trees are larger and more 

 productive than pruned trees. The slender spindle trees are a 

 compromise. The trees have been lightly pruned leaving as many 

 branches as possible without stunting the growth of the central 

 leader . 



Regular-type pruning . The pruning system has been somewhat more 

 time consuming than on the slender spindle trees but less than that 

 for the USDA trees. Yields of the slender spindle and regular- 

 pruned trees were comparable in 1978 and 1979 (Table 2), 



Summ^ary 



The USDA pruning system has been more time consuming than the 

 tier system, slender spindle system, or regular pruning and reduced 

 yields in 1978 and 1979. Heading cuts caused some lateral shoot 

 development on 1-year-old wood but much less than shown in USDA 

 Agriculture Handbook No. 458 following similar pruning. 



At present we prefer the slender spindle system which involves 

 leaving as many branches as possible without stunting the growth 

 of the central leader. 



Recommendations 



At present we will continue to suggest the following for non- 

 bearing trees of standard- type strains: (a) prune as little as 

 possible without dwarfing the central leader; (b) make heading cuts 

 only when necessary to stiffen the central leader or scaffold bran- 

 ches, or to stimulate growth; and (c) spread branches when necessary 



