Pruning

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

EP	Title	# Inst.	Year Establ.
204	Thinning and Pruning: Demonstration Plots	1	1931
205	Thinning and Pruning: Demonstration Plots	1	1931
368	The Adaptability of Tree Species to Forest Sites	1	1958
418	Correlated Curve Trend Studies in Coastal Douglas-fir	1	1952
429	Spacing trials of Douglas-fir, western red cedar and grand fir in pure and mixed stands	1	1964
499	Practical Demonstration of Thinning and Pruning on a Farm Woodlot	1	1954
534	Spacing Trial of Douglas fir	1	1959
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

B.C. Ministry of Forests publications can be downloaded from the following website:
http://www.for.gov.bc.ca/scripts/hfd/pubs/hfdcatalog/index.asp

de Montigny, L. and S. Stearns-Smith. 2001. Thinning and pruning coastal Douglas-fir near Chilliwack, B.C.: 8-year results. B.C. Ministry of Forests, Victoria. Extension Note 56.

de Montigny, L. and S. Stearns-Smith. 2001. Pruning density and severity in coastal western hemlock: 4-year results. B.C. Ministry of Forests, Victoria. Extension Note 51.

Finnis, J.M. 1953. Experimental pruning of Douglas-fir in British Columbia. B.C. Ministry of Forests, Victoria. Research Note 24.

Warrick, G. 1948. Thinning and pruning of second-growth Douglas-fir in the coastal region of British Columbia. B.C. Ministry of Forests, Victoria. Research Note 13.

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Last Modified: 2007 APR 20. Ministry contact: Frank van Thienen
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