Plant Cold Acclimation, Hardiness, and Winter Injury in Response to Bare Soil and Groundcover-Based Nursery Field Management Systems

Abstract

Abstract Effects of five nursery field management systems [cultivation, herbicide management (oxadiazon), legume companion crop (bird's-foot trefoil), winter cereal cover crop/mulch (winter rye), and mixed grass sod (red fescue/perennial ryegrass)] on cold hardiness and the incidence of winter injury were investigated over a seven-year period. Six tree species were included in the research: Fraxinus pennsylvanica ‘Marshall Seedless’, Malus ‘Red Splendor’, Gleditsia triacanthos var. inermis ‘Skyline’, Acer rubrum ‘Northwood’, Thuja occidentalis ‘Techny’, and Picea glauca var. densata. Treatment differences in fall coloration, leaf abscission, and winter injury were observed. Cold hardiness levels were determined for Acer rubrum ‘Northwood’, Malus ‘Red Splendor’, and Thuja occidentalis ‘Techny’ using controlled freezing tests. Species specific differences in cold hardiness development were observed in response to field management treatment: bare soil treatments (cultivation and herbicide management) delayed acclimation and reduced cold hardiness compared to cover crop/mulch (winter rye) and companion crop (bird's-foot trefoil and grass) treatments. Winter injury, which occurred almost exclusively in the bare soil treatments, was limited to Acer and Gleditsia. The types of injury observed included frost cracking, sunscald, branch tip dieback, dieback of large portions of the crown, and complete plant mortality. Compared to bare soil treatments, the presence of cover/companion crops and mulches in nursery field management systems increased plant cold hardiness and reduced plant losses to winter injury. Susceptibility of Gleditsia to winter injury was influenced by Nectria cinnabarina infection which was also influenced by field management treatment.