Effects of Frequency of Chemical Weed Control on Growth and Quality of Christmas Trees1

Abstract

Abstract Effective weed control is essential to the production of high-quality Christmas trees on most planting sites. Many growers use herbicides applied along rows of trees, in combination with mowing between rows, to control competing grasses and broadleaved weeds. This study evaluated one-time, biannual, and annual applications of herbicide during a 6-year period on growth and quality of different Christmas tree species planted on moderately dry and moist planting sites. Increased height growth from more frequent applications was limited primarily to the drier site, and even on that site rotation length would have been reduced by only 1 year. Christmas tree quality, as reflected by foliage density and tree weights, generally improved on both areas as herbicides were applied more frequently. Colorado spruce, Douglas-fir, and Fraser fir benefited more than Scotch and white pines. North. J. Appl. For. 6:15-17, March 1989.