The objective of weed or brush control in commercial forests is to provide increased seedling survival leading to larger, higher quality harvests, and reduction in time required to bring the crop to maturity. Objectives also include protection of wildlife habitat and water quality. In the past 20 years, research has made clear that virtually no other practice will produce as much gain in plantation performance as reducing competing cover, and that careful application of the appropriate chemicals exceeds other methods in safety, cost and habitat protection for most operations.
Weed control alone cannot produce a harvest; it must be combined with cultural practices involving either seeding or planting, and with practices that bring the crop to maturity. Some habitat features involve leaving species other than commercial conifers while favoring the conifers or commercial hardwoods. Growing trees is the ultimate objective, not killing brush; brush/weed control is merely a phase of the reforestation procedure, after which the trees themselves dominate virtually every other kind of plant where they grow. Selective vegetation control is an efficient method of enhancing certain kinds of wildlife habitat.
Weed control enhances conifer survival and growth. On harsh sites in southwestern and eastern Oregon, almost total weed control is essential even to obtain survival, and it may be necessary to maintain a weed-free site for more than two years. On better sites in the Coast Range, although initially weeding may not be essential for survival, fast-growing herbs and brush will threaten survival within a few years. Treatment to prevent onset of brush problems will greatly enhance productivity. Indeed, weeding pays best on the best sites, even though the percentage increase is greatest in poorer sites.