Time to trim those trees?

Trees with bountiful branches are both a bane and a boon for the urban homeowner. Their growth rates vary, but invariably trees become unruly and require discipline — just like children.

The difference, of course, is that, with trees, corrective techniques usually are more drastic. Arborists believe in pruning and occasionally cutting down — “taking down” in trade lingo — trees in order to promote health and protect property. Among other skills, most arborists also are trained to diagnose disease and direct planting as well as removal of trees and other greenery.

None of this is done easily. Nor is it cheap. A pruning job done by professionals certified by the Illinois-based International Society of Arboriculture can cost hundreds of dollars. Taking down a problem tree can cost upward of $2,000, depending on size, location and challenges involved.

Meredith Gonyea, of Quesada Street in the District, had neglected the trees on the grounds of her Georgian Colonial brick home for many years until one massive oak in the back yard and a smaller one in the front grew dangerously close to the house.

The tree in front required removal because its roots were threatening the very foundation of the house. The tree in back needed pruning — drastically — since at least one large limb was touching the roof.

It was her first time working with a professional service — those whose employees are bonded, as opposed to the self-styled “tree expert” who arrives unannounced at the door with a pickup and chain saw.

She asked three companies to give her estimates, which usually are free, and chose Branches Etc. of Kensington (www.branchestreeexperts.com).

“I liked their approach and found them reasonable,” she says. They arrived one recent morning at 9:30 with a supervisor and a crew of four, plus a powerful machine called a chipper that can chew up downed wood with ear-deafening precision.

First order of the day for the oak in back was for experienced climber Santiago Martinez, 45, to position several ropes high up in the crown. This enabled him to reach above and cut or trim branches and limbs, lowering himself as he gradually worked downward with a size 21 chain saw under the guidance of arborist Matthew Madiera.

Mr. Martinez hauled himself up by hand and threw ropes over successively higher limbs until he was able to begin cutting. The ropes are a safety line as well as the means of controlling each limb when it is cut. (It is illegal to use shoes with spikes since they would make holes and harm the bark.)

A cut limb is dangerous when it falls since each section can weigh as much as 50 pounds. Craftsmanship comes in knowing where to place a rope so a limb falls in the right place. Balancing on one limb while cutting off another, an experienced aerialist resembles a circus performer whose tent is the sky.

During the previous week, working on 2 acres of wooded property in Bethesda, the same crew had taken down a black oak that was 60 feet in height and 3 feet in diameter. Its age was an estimated 130 years. The job had taken a day and a half.

Branches Etc. had been watching the tree for years and taking care of the family’s property for 10 years. Company President Michael Guercin knew the tree had been slowly weakening — possibly diseased by carpenter ants — and even had stopped producing leaves.

The current season is a busy one, but Kevin Carr, the manager of the Rockville office of Bartlett Tree Experts, a national firm, sees business drop off slightly during the fall-winter period because many homeowners mistakenly assume it isn’t a good time to do pruning work.

“Most tree pruning is acceptable any time of year as long as you have good pruning techniques,” he says, noting that for some species it is best to avoid the flowering season.

Elms and fruit trees are among the species that are vulnerable if pruned in the spring, says Mr. Guercin, because the beetle that causes Dutch elm disease is attracted by the pheromone secreted by the trees at that time.

It is a myth, he asserts, that trees are made vulnerable and liable to fall in a strong wind or hurricane because the soil is loosened by accompanying torrents of rain. More damage is caused by the wind itself when it blows above 50 miles an hour, he says.

Pruning the crown and opening it up by removing dead and weakened limbs helps reduce wind resistance by creating a better structure, Mr. Guercin adds.

Another problem occurs when trees are planted in tree boxes he calls coffins because they have a limited root zone.

“Roots extend out three and four times beyond the drip line of outer branches,” Mr. Guercin says. “Roots can go underneath some substances but with concrete they have a difficult time.”