(41) FORMATION AND MANAGEMENT OF PLANTATIONS - NURSE TREES IN PLANTATIONS

The next point to be considered is that of introducing nurse-plants into plantations. That these have a tendency to accelerate the upward growth of trees for a number of years there can be no doubt, but it is at the expense of the side branches and leaves. Evergreen nurses, such as the scotch, silver, and spruce firs, improve the condition of a plantation by preventing the radiation of heat from the ground, by checking the growth of herbage, and by protecting the principal trees from high winds winds until they are thoroughly established in the plantation. The kind of tree which is to form the main crop having been fixed on, and the number that when full grown will stand on an acre or any given surface, they should be planted in their proper places, and the intervals filled up with the nurse-plants. As the nurses grow, and their branches touch the principals, let them be thinned, so as not to prevent the free growth of the principals: this should be done gradually. For example, it is customary to plant oak with coniferous nurses, and in the course of seven to ten years the nurses require a partial thinning to make way for the principal trees; at this date the pines will be fit for poles or rails. It often, however, happens that the nurses are allowed to remain too long, and the principal crop consequently suffers from the evils of overcrowding.






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