The Real Christmas Tree Board

Christmas tree growers across the country are looking for strategies to improve tree survival following planting. In the Pacific Northwest, tree survival has been worsened due to longer, hotter, and often drier summers. The premium tree species in the region, noble fir, has been particularly sensitive and subject to, in some cases, complete plantation failures. Both researchers and growers have been investigating approaches to improve planting success. The varied approaches include applications of anti-transpirants, water absorbing gels, fertilizers of all types, mycorrhizae dips, plant and root stimulants, shading, and a wide assortment of root dips and sprays. This study, funded by the Real Christmas Tree Board, evaluated four treatments during one year after planting noble fir at three sites. Treatments were- Fall vs. Spring planning, Biochar applied as a top dress at planting, fertilizer “tea bag” additions to the planting hole and coarse wood mulch as a top dressing. To quickly summarize results, rabbits destroyed the fall planting, despite our high hopes. Rabbit damage is not unique to fall plantings. Our trees just happened to be in the wrong place and the rodents failed to grasp the importance of the research. Biochar and fertilizer tea bag additions were the second and third treatments evaluated. The fertilizer treatments had shown promise in a prior experiment in a year with significant spring rainfall. The Biochar addition was a new treatment that touted improved soil moisture status. In our 2023 trial, neither of these treatments provided improvement in either tree growth or survival. That leads us to the fourth treatment- coarse mulch spread around the trees (approximately 1.5 gallon/tree). This treatment improved survival percentages and had a slight improvement in tree growth. Across the three sites in this experiment, mulch increased survival by 22%. But we saw different survival ranges at the individual sites. At one location, mulch provided only a 4% improvement (to 65%). At another location, mulch provided a 46% improvement (to 48%). At the third site, mulch provided an 18% improvement in survival (to 97%). Of all the products/treatments we have evaluated, mulch has provided the most consistent tree survival results. Mulch mitigates high soil temperatures and conserves available soil moisture. Yet mulch can only do so much so, a few growers are improvising dryland irrigation strategies. Kirk Stroda, a grower in Monroe Oregon, has devised two irrigation techniques on his farm. A video will be available shortly at https://agsci.oregonstate.edu/nwrec/programs/christmas-trees. The challenge for growers will be balancing the added costs of mulch and/or watering vs. costs of replanting, delays in tree harvests and missing trees.