City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: https://read.dmtmag.com/i/94460
Plant Growth Regulators for Urban Forest Management: The Sacramento Model Story and photos by Gordon Mann, Mann Made Resources Consulting of line-clearance pruning. Costs include the price of material and application, any environmental impact, and any damage to or reduction in useful life of the tree. The benefits can include reduced pruning cycles, fewer future pruning wounds, tighter and denser foliage growth, enhanced fibrous root production, enhanced views, better visibility of traffic control devices, and decreased maintenance for utility line clearance. Plant growth regulators (PGRs) can aid in the effort to reduce the frequency As a municipal arborist in Redwood City, California, I was challenged by the trees and utility line competition. Approximately 30% of Redwood City's street frontages had overhead utility lines. Tiny lollipop trees did not seem a viable approach. Eliminating a shade canopy on 30% of our community's streets was not acceptable per our urban forest management goals. Also, I did not want the utilities to have to prune our trees with the style they were using to achieve required clearance. The approach Redwood City followed was to designate shorter, decurrent trees under the power lines. Then we pruned to direct growth so the branches would grow under and around the transmission lines, creating a larger crown while meeting required clearance—without cycle-driven line clearance pruning. If I was still there, I would use PGRs on well-pruned trees under power lines to avoid the need for utility pruning altogether. I had the opportunity to visit and observe the Sacramento Municipal Utility District (SMUD) vegetative management program staff as they applied plant growth regulators (PGRs). SMUD serves primarily Sacramento County, California, and some other out-of-County locations. It was fascinating to observe the extent of experience and expertise that SMUD has with PGRs, which they initially used to reduce tree- related power outages and enhance system 30 Short internodal growth on PGR-treated pear reliability without removing trees. But first, a little background. Trees are highly valued in the Sacramento region. The Sacramento Tree Foundation's Greenprint Initiative seeks to double the canopy of the Sacramento Area Council of Governments' six counties by 2040 to improve air quality. Sacramento County is the most populated county in the region, and retaining trees around its utility lines is important to achieving the canopy goal. However, many trees do not have sufficient laterals to which one can prune back at the necessary clearance distances. Once trees are severely pruned, they often respond with (right) Dense shortened node growth on Deodar cedar City Trees