urban forestry

In Mt. Lebanon, we take our trees pretty seriously. Mt. Lebanon is a Tree City USA, which means we meet the specific criteria set by the Arbor Day Foundation. Tree Cities must have a tree board or department, a tree care ordinance, a community forestry program with an annual budget of at least $2 per capita—this year we’re spending about $14—and an annual Arbor Day observance or proclamation.

In 2016, more than half of the public works department’s 1,099 requests for service—602—were related to trees. The next highest category, requests related to storm and sanitary issues, totaled 87.

Mt. Lebanon has about 11,000 street trees and about 10,000 more in parks. A budget of $469,930 takes care of planting, trimming, maintenance and disease control, most of which is done by a three-man forestry crew.

Calls for service outpace the crew’s ability to stay abreast of the work, since the foresters also must work on other public works projects, such as leaf collection and snow and ice control. Most of Mt. Lebanon’s street trees can only be pruned during their dormant season in the late fall and winter. Even with the inclusion of $45,000 in the budget for hiring outside contractors to work solely on dormant-season pruning, some of the requests can take up to a year for a response.

The forestry crew’s workload increases after a storm or other severe weather event.

“The crew handles all the storm damage,” says public works director Rudy Sukal. “And we get calls to evaluate the health of trees.”

A new technology, sonic tomography, enables the foresters to assess the health of trees without having to drill into them. 
Sonic tomography enables foresters to detect the size and location of decayed or hollow regions in a tree trunk without harming the tree. It works based on sound velocity measurements between several sensors around the trunk.

“It’s like an ultrasound for trees,” says Sukal.

Along with tomography, foresters use a minimally invasive tool called a resistograph, a micro-drill that measures the density of wood throughout the tree. If the drill reaches softer, less dense wood that offers less resistance, that is an indicator of interior rot.

Other forestry efforts include the fight against the emerald ash borer, an invasive insect that came to the U.S. from Asia about 10 years ago. About 400 of the infected trees have been removed, and the remaining ashes have been treated with a vaccine that protects them from the virus for up to two years.  The vaccine, called Tree-age, is injected under pressure into the trees’ trunks and will protect healthy trees from the ash borer for two years. The program has been going on for the past seven years and has preserved about 700 to 750 ash trees. The alternative, Sukal says, would have been to remove all of the more than 1,000 trees at once, at a cost of about $750 to $1,000 per tree, plus the cost of replacing them.

Mt. Lebanon purchases trees in bulk and keeps them at a nursery at the public works facility on Cedar Boulevard. If a municipal tree in front of your house dies (either on the tree lawn-—the strip of grass between the street and the sidewalk—or, if you have no sidewalk, in the 10-foot right-of-way from the street), the municipality will replace it at no charge. If you do not have a tree in front of your house, you may purchase one and have it planted for a total cost of $155. 

Mt. Lebanon only plants trees in the fall, when the tree doesn’t need as much watering and the soil is still warm enough to allow some growth before the tree becomes dormant in the winter.

To request a tree, leave a voicemail at 412-343-3403.The forestry crew will select the most suitable spot and type of tree for your location, taking into consideration factors such as proximity to utility wires, possibility of obscuring the view for drivers and pedestrians, and the possibility of roots damaging sidewalks or underground pipes.

Choosing a tree that will fit into the municipal landscape is not easy. The tree’s suitability to the environment and its growth habits need careful consideration, Sukal says. Trees can’t grow so tall that they interfere with power lines. They can’t grow so wide that they interfere with traffic and force pedestrians into the street. They can’t spread roots so extensively that they ensnare sewer lines. And finally, a tree needs to able to survive in this zone’s soil and weather conditions and be resistant to road salt.

The majority of street trees the crews are planting now are hedge maples and a few lilacs.

“Our guys are pretty good at analyzing a tree’s health,” Sukal says. It’s much easier to leave a tree in place and to take care of it, but at some point we have to make the decision to remove some trees for safety reasons. Safety is our primary concern.”