The Real Christmas Tree Board

Fraser fir is among the most popular conifers grown for Christmas trees in the United States due to its form, needle color, scent, and needle retention. However, Fraser fir trees produce copious quantities of cones, which are a significant challenge for producers as cones must be removed by hand, resulting in a major labor investment. In this trial we investigated the utility of applying a plant growth regulator (paclobutrazol) to reduce cone production in Fraser fir trees at three Christmas tree farms in Michigan. Trees in the study were 1.3 to 1.6 m (4.3’ to 5.2’) tall at the start of the trial, depending on the farm. We found that paclobutrazol, applied either as a one-time soil drench or as an annual foliar spray, reduced cone production for up to four years after initial application. Paclobutrazol also reduced leader growth, which could provide an additional benefit to growers by producing more compact trees with less need for shearing. However, application rates used in this trial resulted in over-regulation of growth and the production of terminal leader that were shorter than growers would desire. Moreover, we observed a loss of straightness in terminal leaders of trees as application rates increased. We suggest additional trials to investigate the benefit of applying lower rates of paclobutrazol earlier in the crop rotation to provide growth control, reduce coning, and minimize potential negative effects of over-regulation of growth and loss of tree straightness.