The arboricultural and economic benefits of formative pruning street trees

Abstract

Research was undertaken to determine the need for, and costs of, formative pruning recently planted street trees. Specimens of Corymbia citriodora (48), Platanus × acerifolia (104), Pyrus calleryana (79), Quercus palustris (65), and Ulmus parvifolia (52) were surveyed. Health was similar for all species, but form and structure varied. Data showed that codominant stems (68%) and included bark (40%) in the canopy or trunk were by far the most common structural defects. Codominant stems were reported in 92% of all Ulmus parvifolia, 66% of Quercus palustris, 61% of Pyrus calleryana, 44% of Platanus × acerifolia, and 19% of Corymbia citriodora. The number of trees of a species that displayed no structural defects was 25% or less except for Corymbia citriodora with 60% showing no structural defects. The pruning required to rectify these structural defects was recorded and then multiplied by a time factor for pruning with secateurs (hand pruners), a handsaw, or a pole pruner. Total time was then converted to an economic cost using current labor market prices. Platanus × acerifolia required the most work per tree with a final formative pruning cost of AUD $4.13 followed by Ulmus parvifolia ($3.25), Pyrus calleryana ($2.76), Quercus palustris ($1.62), and Corymbia citriodora ($0.99). This compares with an average cost of $44.59 per tree for structural pruning 20 year old trees. Formative pruning makes sound arboricultural and economic sense. © 2013 International Society of Arboriculture.