ASHS 2024 Conference

In the Great Lakes region of the United States Christmas tree plantations are established by planting seedlings or transplants. Reducing plant moisture stress after planting is crucial to successful establishment of these small conifers. A myriad of products have been marketed to Christmas tree producers with claims to improve transplant success by limiting transplant shock. Since 2021, we have conducted a series of field trials in collaboration with Michigan Christmas tree growers to evaluate the effect of root dips, mulching and other cultural practices on transplant survival and growth. Root dip products applied immediately prior to planting included: DieHard™ Root Dip (endo/ecto mycorrhizae polymer), MycoApply® Injector Ecto (ectomycorrhizae), SoilMoist™ Fines, and Roots® Terra-Sorb® Fine Planting Gel (polymer). Cultural treatments that were applied following planting included: foliar antitranspirant spray (Wilt-Pruf® [25% di-1-p-menthane]), wood chip mulch, shade blocks (20.3 cm x 30.5 cm mesh screen), controlled release fertilizer, and biochar. Root dips did not affect tree survival or growth in any of the trials. Mulch and shade blocks increased shoot growth at several farms. Improved survival of trees under mulch was associated with improved soil moisture. Mulch did not affect foliar nitrogen (N) concentration, indicating that mulch did not ‘tie-up’ N. The application of Wilt-Pruf reduced transpiration but also reduced photosynthetic rate, resulting in a net decrease in shoot growth. Fertilization at planting significantly reduced survival on two of four sites. Overall, the results suggest that cultural treatments, especially mulch, are more likely to improve plantation establishment than root dips.