Table 4.--GrcnJth of sample trees in the first and second 5-year periods after pruning 





Height 



Diameter 



Treatment ^ 



Average annual 





Average annual 





growth of 



: Pruned trees^ 



growth of 



: Pruned trees^ 





unpruned trees 





unpruned trees 







0-10 years 



: 0-5 years : 5-10 years 



0-10 years 



: 0-5 years : 5-10 years 





Feet 



- - - - Percent - - - - 



Inches 



- - - - Percent - - - - 



1 



1.2 



48** 76** 



0.21 



50** 69** 



2 



1.2 



67** 88** 



.22 



69** 81** 



3 



1.2 



76** 88** 



.21 



74** 78** 



4 



1.1 



82** 97 



.20 



86** 105 



5 



.9 



86** 114 



.17 



84** 109 



^For description of treatments, see page 3. 

 ^Expressed as a percent of the unpruned tree growth. 

 **Significantly different than the unpruned paired trees as determined by "t" tests 

 (1 percent confidence level) . 



The most severe pruning treatment --where the lower two-thirds of the green crown was 

 removed- -reduced height growth in the first 5 years to about half of its previous rate. 

 The other pruning treatments demonstrated similar but proportionately less reduction. 

 Diameter growth responded the same as height. 



The trees gradually recuperated from the effects of pruning. Although all treat- 

 ments reduced growth considerably the first 5 years after pruning, only the more severe 

 pruning had any significant (t-test, 1 percent confidence level) effect during the 

 second 5-year period. Even the most severely pruned trees gradually regained their 

 normal height growth--from about 50 percent of normal in the first 5 years to 76 percent 

 in the second 5-year, period. Diameter growth rates returned to normal more slowly than 

 did height growth rates. 



Production was nearly identical on pruned and unpruned trees (table 5) . The two 

 treatments in which half of the crown was removed appeared to increase production during 

 the first 5 years after treatment, but these differences were not statistically signifi- 

 cant because of considerable variation in response. About one-third of the sample trees 

 produced Christmas trees during the first 5-year period after treatment and another 

 third during the succeeding 5 years. 



No differences in tree grade could be detected between pruned and unpruned trees 

 using any of the pruning methods. Approximately one-third of the merchantable Christmas 

 trees produced were standard-grade trees and the other two-thirds were utility-grade 

 trees (table 6). Only a few premium trees were produced in all of the paired samples. 



About one-third of all the trees were classed as culls. The following accounted 

 for about 90 percent of the culling: crowns were too open, 70 percent; and trees damaged 

 by Christmas tree blight, 20 percent. Suppression, deformities, and poor balance caused 

 the remainder of the culling. Mortality was light in both pruned and unpruned trees. 

 Only 4 percent of the pruned trees and 1 percent of the unpruned trees died during 10 

 years following treatment. 



About two-thirds of the merchantable trees produced were in the 6- and 8-foot 

 classes (table 7). Most of the others were in the 2- and 4-foot classes; 10- and 12- 

 foot trees were rare. 



9 



