Notes From The Field: Urban Forestry

The work of the department’s urban forestry group involves many different facets, but the main purpose of our work is to care for the trees found at our trailheads and along trails in the eastern half of the county. This team’s responsibilities have evolved to include many duties associated with tree care such as planting, irrigation installation, pruning, and removals.

Planting

It all begins with planting. We plant everything from very small container trees that can be hand planted to very large balled and burlaped (B&B) trees that can be planted only with specialized equipment. Over time, the tools we use to install these larger trees have evolved. In the beginning, it was a single person using a large dolly and human strength to maneuver trees into place. Now we use a tree caddy built in the weld shop that attaches to the forks or bucket on a Toolcat machine. It then hooks directly onto the wire cages that encase the base of B&B trees to safely and easily transport them. Using this tool, we can get the larger trees unloaded, transported across planting sites, and set in place without having to overexert staff or volunteers. It also means we can plant more quickly, getting more large trees in the ground in a day than when using the dolly method.

Tending

“Caring for the trees is our job, but it is also our passion, and we are glad to do our part to make our trailheads and trails spaces everyone can enjoy.”

Once the trees are planted, it is urban forestry’s job to ensure that they get enough water to establish roots. In some places we have permanent irrigation systems that run year after year. Other systems are temporarily installed with the intention of removing them once roots have been established. We check the irrigation systems each spring to ensure water is flowing properly after a winter of freezing and thawing cycles, and run every system on a timer that controls the watering schedule. Over the course of the year, we adjust those timers to account for seasonal changes in temperature and precipitation. Once watering season is over and the plants go dormant, we blow all the water out of the systems with an air compressor to ensure water will not freeze and expand in the system, causing it to rupture and break. We will also temporarily hand-water trees in locations without irrigation until they are established. To supplement our watering efforts and to incorporate organic matter into the soil over time, we also put mulch rings around the base of the trees to prevent water loss from evaporation after watering and rain events.

Directing Growth

After trees have been in the ground for a year or longer, we prune them in ways that will encourage growth in the directions we want, based on where that tree is planted. For example, we prune trees planted in parking areas to grow up, instead of out, to avoid branches interfering with parking spaces. We will also prune to improve airflow through the crown of the tree, to remove branches growing at odd angles or into neighboring branches, and to mitigate the risk from dead or dying branches falling on the trail below. If a tree experiences substantial dieback or experiences a traumatic event (like frost damage) that kills it, we might remove the tree if it is in a place where it could fall and cause injury or if it was originally planted to provide shade by a picnic table or bench. If it can safely be left alone and doesn’t need to be replaced, we leave the tree as is and let it die to become valuable habitat for wildlife.

While this article doesn’t cover all of urban forestry’s functions, which also include things like educational outreach and invasive species management, it is a pretty good look at what we do for the trees in open space. Caring for the trees is our job but it is also our passion, and we are glad to do our part to make our trailheads and trails spaces everyone can enjoy.