More often than not, when Duke Energy cuts trees limbs back from its power lines, the neighborhood email lists light up with dismay and complaint about how little is left.
There is, though, a way to make those periodic tree trims less drastic, according to Lee Pardue from Duke Energy and Brandon Hughson from the Rainbow Tree Care company in Minnesota. They spoke to the InterNeighborhood Council meeting about it last week.
It’s called Cambistat, a chemical that slows the tree’s growth rate while stimulating the tree to grow more roots – resulting in a healthier tree that needs less trimming to keep out of Duke Energy’s cables.
That would be particularly beneficial for the willow oaks along the streets in older neighborhoods where, with trimming, “the sensitivity issues tend to arise,” Pardue said, and where aging trees are already under stress from their urban environment.
Duke Energy isn’t using Cambistat in Durham, but the company suggested its use during a meeting with some city officials under some recently trimmed trees on Duke Street, he said.
“I was horrified at the amount of wood that was being taken off the trees,” said City Councilman Don Moffitt, who had contacted city arborists and the power company to talk about the situation.
Cambistat reduces a hormone that stimulates a tree’s growth up and out and increases a hormone that stimulates root growth – important for willow oaks whose roots are typically restricted by pavement and hard-packed earth.
It also stimulates a tree to grow thicker, darker leaves than it would otherwise, increases flower and fruit production, and improves resistance to some diseases, Hughson said.
Cambistat is injected into the ground a few inches from the tree trunk, and remains in the soil close to where it’s applied, Hughson said, responding to a question whether it could drain into groundwater that ends up in reservoirs. One treatment is good for about four years, after which a treated tree resumes normal growth.
At Moffitt’s request, the city-county Environmental Affairs Board investigated Cambistat and in July gave it a qualified positive report.
“The EAB is convinced that Cambistat is safe when used appropriately. However Cambistat should not be considered a long-term or all-encompassing solution for trees that are growing beneath and nearby power lines,” the board’s report said. “We would also like to re-emphasize the importance of sufficiently informing nearby property owners and ensuring the proper application of Cambistat.”
Now, Duke Energy is putting the idea out to the public.
“It’s not a sales spiel,” he said. “We’re just taking baby steps, walking through to see how you guys feel about this.”
Duke Energy is entitled to keep limbs away from its lines, but the company won’t try Cambistat without the city’s OK, Pardue said. Cambistat wouldn’t be used on trees on private property without the property owner’s consent, nor on a city-owned tree in front of a home without consulting the resident.
“This whole program is designed for us to work closely with the community as a positive thing so that you’ll have more of your biomass and (we will) not be removing so much when we come out,” he said.
Cutting back a tree puts the tree under stress; minimizing the amount of wood taken off would lessen the effect on Durham’s aging willow oaks, which were planted about 80 years ago and are reaching the end of their natural lifespan. Less pruning, Pardue said, is “buying time” for them.
Pardue and Hughson and Cambistat got no endorsement from the InterNeighborhood Council, but the delegates were not critical, either, and at the end they got a polite round of applause.
Moffit, speaking on a separate occasion, said Duke Energy does have to overcome public suspicion of chemicals, and before supporting Cambistat said he would want assurance that Duke Energy would not use it to increase the intervals between prunings – which might mean taking off the same amount of wood, only less often.
“My goal is to do the best we can to protect our canopy of willow oaks as long as possible,” he said.
“It’s not just beauty. Having the trees reduces the temperature in the city and has a whole host of benefits toward public health,” Moffitt said. “No matter where you live in the city it ’s important that we nurture them as long as we can.”