IMPROVING NURSERY PRODUCTION AND LANDSCAPE ESTABLISHMENT OF HICKORIES AND OTHER TREES FOR URBAN FORESTS

Abstract

Hickories (Carya spp.) have long been sought after by horticulturists for their ornamental traits yet have not been integrated into commercial nursery production due to limited propagation techniques, slow growth, and claims of poor transplant success. Further, their environmental tolerances and potential uses in managed landscapes have been speculative, traditionally based on observations of their niche roles in the wild. A series of experiments were conducted with the goal of characterizing drought tolerance and identifying alternative propagation and production techniques that could bolster cultivation of hickories in the nursery and ease establishment into the landscape. Drought tolerance of multiple desirable species was predicted and ranked to guide the matching of taxa to the site conditions they are best suited, while also providing evidence of variability between individuals and provenances to support the selection of superior clones. A modified-stool-bed-layering technique was assessed for successful asexual propagation and found to be well-suited to shagbark hickory. The use of GA4+7 to increase the rate of development of seedling hickories was tested and determined to be effective for bitternut hickory and pecan. Container production of hickories in standard plastic nursery pots and RootMaker® bags was trialed against field production of liners and shown to be an effective means of growing bitternut hickory and kingnut hickory. Symptoms and susceptibility to mouse ear disorder, a function of nickel deficiency, were characterized and documented for the first time in bitternut hickory. The disorder was successfully corrected using the commercial product Nickel Plus®. In addition, a series of transplanting regimens involving trees of several species and representing different nursery stock options were implemented at the Bluegrass Lane Turf and Landscape Research Center on the Ithaca campus of Cornell University to document plant recovery and provide physiological evidence to help explain transplant success of hickories in the landscape. Separate from the research involving hickories, three experiments were conducted using unrelated taxa to better understand the influence of root pruning on root hydraulic conductance in field production and with container-grown nursery stock as well as exploring mouse ear disorder in two underutilized species of Betula.