Stages in Branch Development and their Relation to Pruning

Authors: G.S. Brown
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1959, Issue N.Z.J.For. 8(4) 1962, pp 608-622, Jan 1962
Publisher: New Zealand Institute of Forestry

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Abstract: The manner of development of those parts of the branches of Pinus radiata that are eventually embedded in the tree stems as knots is described, and it is shown that in plantation conditions there is first a phase of rapid diameter growth, followed by a second phase about twice as long during which the diameter remains almost static although the branch is alive. It is argued that because it is during the first phase that, the greatest proportion of the stem perimeter is occupied by the branches, it is also during this phase that the greatest risk of physical damage from pruning exists; and further that because this phase only occupies about one third of the potential life of the branch, pruning at or before its culmination must be regarded as severe pruning whether related to risk of physical damage or to possible damage of any other kind. A relationship between the duration of the first phase of growth and branch diameter is suggested as a basis from which can be calculated the minimum amount of green crown that can be left at any pruning without encroaching on the first phase of branch growth. This is suggested as a supplementary check on pruning severity when a heavier than usual degree of pruning is contemplated.

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