Red Maple and Silver Maple Growth Evaluated 10 Years After Application of Paclobutrazol Tree Growth Regulator

"Trees treated with soil-injected paclobutrazol tree growth regulator (TGR) were compared to untreated trees 10 years after treatment. Red maple and silver maple were treated in 1984, 2 months after being trimmed, with 0.5, 1.0, or 2.0 g of active ingredient (gai) per inch diameter at breast height (dbh). The volume of delivery varied for silver maple (300, 1500, or 3000 mL per tree); however, red maple were all treated at 1500 mL per tree. The untreated trees required trimming again in 1988 and 1990. No information was collected at these trimming dates. All trees, treated and untreated, were then trimmed in 1994; the biomass removed and the time taken to trim and chip the trees were recorded for each tree. Treated trees had significantly less biomass removed than did untreated trees. Considering that the untreated trees had been trimmed an additional two times, further separation between the treated and untreated trees was evident. Reductions in biomass correlate well with reductions in time required to trim the trees and chip the biomass removed. Differences among application volumes demonstrated the importance of proper TGR placement for best results. At higher application volumes, there were no significant differences between the 1- and 2-g rates."