THE PRUNING OF WHITE PINE 



By F. B. KNAPP 



DiBECTOB OF THE EBIC FoEEST SCHOOL 



^^<'HERE is a widespread theory among both American and German for- 

 L) esters that live branches must not be cut from evergreens. As the 

 result of experiments by Mr. Nathaniel Morton, of Plymouth, Massa- 

 chusetts, begun in 1891 and later investigations by the Eric Forest School, we 

 hold exactly the reverse position with reference to white pine at least, and are 

 convinced not only that such pruning can be successfully done but that it 

 should form the basis for the treatment of our woodlands in many places. 



Each system of silviculture has its distinct use and must make certain 

 sacrifices to attain its ends. Our aim is to secure a fair quantity of large, 

 clear, high-grade timber with a short rotation. To accomplish this we pay 

 special attention to a small number of selected trees from the beginning. In 

 the first stage of growth obtain by pruning and thinning a tall slender tree 

 with clean bole of moderate length; then get a rapid diameter growth by 

 keeping the remaining branches alive and enlarging the head to its -full 

 capacity. 



Mr. Morton read a paper before the Massachusetts Forestry Associa- 

 tion in 1899 telling what he had accomplished and describing his methods in 

 detail. He found that the best time to prune the living branches of the white 

 pine was in the hottest summer weather. The branch is cut off close to the 

 bole of the tree; sap flows copiously at first but is quickly seared over by the 

 heat, thereby sealing the wound against di.sease and preventing the streak of 

 pitch so often found after winter trimming. The wound heals quickly by 

 occlusion with no space or pitch pocket at the end of the small tight knot, and 

 almost immediately outside of it the wood becomes clear and straight grained. 

 As a fair sample of what we have found, the first piece of the Morton trees 

 analyzed by us showed fifteen knots without a single one which failed to come 

 up to this standard. Where a dead branch has to be taken off the cut is made 

 deep enough to wound the living cambium entirely around the knot in order to 

 produce the same quick recovery. For when a dead branch is broken or cut 

 off without such wounding the growth is apt to continue for some years, much 

 as though the branch were still there, forming a little tunnel to collect pitch 

 and dirt. 



During the first two years the proper amount of protection, light, air, 

 and soil are maintained and a single leader secured for each selected tree and 

 the neighbors are made subservient to it. When from four to eight feet high 

 the pruning of live branches is begun, leaving the head about one-third of the 

 height of the tree. This pruning of live branches and the protection from 

 competitors is continued through the first period of growth. Not over two 

 whorls are taken off in any year. At the end of this time we have a tree with 

 a slender bole, no dead or sickly branches and a small but well developed 

 head, closely surrounded though not crowded by more stocky trees. A typical 

 tree with an eighteen-foot bole would be twenty-seven feet high with nine feet 

 spread of ci-own, a diameter of four inches breast high and between two and 

 three inches just below the first branch. 



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