Pruning Research

Pruning of lower branches of trees in plantations and in pre-commercially thinned stands can increase stand value by reducing the size of the knotty core, thereby increasing the amount and proportion of more valuable clear (knot free) wood. Dimensional lumber that is "clear" of knots and defects has historically commanded premium prices on world markets. Pruning may also improve log and lumber value by speeding the change from lower value juvenile wood to higher value mature wood, and by reducing stem taper 

Pruning severity refers to the amount of live crown removed during the pruning operation. Tree growth may temporarily decline following live crown removal, and the magnitude of growth decline likely increases with pruning severity. Decisions regarding when to prune and how much live crown to remove must balance possible growth reductions with the desire to maximize the amount of clear wood production. 

Pruning density refers to the relative number of trees pruned within a stand. Simple economics favours pruning only the crop trees that will survive until final harvest. However, pruning only some of the trees in a stand may put pruned trees at a growth disadvantage compared with unpruned trees, possibly even threatening their status as future crop trees. 

Pruning is a very costly silvicultural treatment. The biological factors affecting the development of pruned stands must be thoroughly understood to ensure that the desired objectives are achieved and that investment returns are maximized. Experimental projects (EP's) testing a variety of pruning severities and densities have been established by the BC Ministry of Forests, Research Branch in coastal managed forests. The earliest pruning field experiment was established on Vancouver Island in 1930. 

Experimental Projects - Coast

Experimental Project # Title # Installation Year Established
204-205 Thinning and Pruning: Demonstration Plots 1 1931
499 Practical Demonstration of Thinning and Pruning on a Farm Woodlot 1 1954
1065.01 Pruning young Coastal Douglas-fir 3 1990 - 1991
1065.02 Pruning Coastal western hemlock 3 1992
1065.03 Pruning western red cedar 1 1994
1065.04 Pruning Sitka Spruce 4 1994

Pruning Publications