Quercus virginiana Mill. (live oak) trees produced in in-ground 61 cm (24 in) diameter fabric containers were overhead misted and given root ball irrigation after harvesting during early summer. Duration and frequency of overhead misting was reduced to zero over a 3 week period. Water potentials (ΨT) were measured diurnally and osmotic potentials measured from leaves at midday. Intermittent overhead misting was as effective as continuous overhead misting in maintenance of ΨT above −1.0 MPa. Water potentials of −1.5 to −2.0 MPa were measured when the period between overhead misting was expanded from 30 min to 45 min. Osmotic adjustment occurred only in trees receiving overhead misting. Trees receiving only root ball irrigation developed ΨT below −2.5 MPa within 5 days after harvesting. After 3 weeks, ΨT and osmotic potentials were the same for all treatments. In a second experiment, trees were root pruned inside the fabric container 11 weeks before harvest. All root pruned trees survived acclimatization, but only 50% of unpruned trees survived. Water relations were similar to trees in Experiment 1. Surviving trees, both pruned and unpruned, had a significantly higher percentage of fine root weight (roots < 2 mm diameter) than trees that did not survive.
Florida Agricultural Experiment Stations Journal Series No. R-01903.
3Associate Professor, Department of Environmental Horticulture, University of Florida, IFAS, 1545 Fifield Building, Gainesville, FL 32611-0512