Young trees sometimes lean, or topple by pivoting about a point below the ground. Geotropic curvature in the lower part of the stem restores the leading shoot to the vertical. The resultant stem bowing reduces potential lumber recovery, and is associated with reaction wood formation. Toppling has occurred in lodgepole pine (Pinus conforta Dougl.) plantations throughout British Columbia. Generally the number of trees affected has been small; although in the southern interior of the province the majority of trees in some plantations have toppled. In areas where toppling in planted trees has occurred, naturally established lodgepole pine is relatively stable. Since planted trees are usually of the native provenance, this suggests that toppling in plantations is primarily the result of nursery and planting effects on root morphology. More normal root morphogenesis, and hence greater stability can be achieved by planting young seedlings that retain the capacity to initiate primary lateral roots. Pruning the lateral roots of older stock provides another approach. A chemical method for pruning lateral roots of container-grown lodgepole pine seedlings has been developed and adopted commercially in British Columbia and elsewhere.

Conifer seedlings of 10 species from 6 genera were raised in containers coated on the inside with basic cupric carbonate in latex paint. The copper paint prevented lateral roots from growing down or around the container wall. After transplanting, the chemically root-pruned stock was capable, in most cases, of vigorous root growth. The effectiveness of the chemical root pruning treatment varied with species, container size, growing medium, and the concentration of cupric carbonate in the container wall coating.