Ask Nykia Perez why she and her friends are running around Kensington planting trees, and her eyes plead, "You're kidding me."

"OK," she says. "I mean, it's great we have Fairmount Park. But Fairmount Park isn't in Kensington."

Spend some time with Perez, Dina Richman and Jacelyn Blank - librarian, entomologist and teacher, respectively - and you'll soon believe, as they do, that it's only a matter of time before their neighborhood streets are lined with honey locusts and chokecherries, red maples and serviceberries.

Maybe not Fairmount Park, but getting there.

In spring 2007, the trio became Philly Tree People, one of 135 neighborhood groups that have planted more than 20,000 trees in Philadelphia and the four suburban counties surrounding it in the last four years.

"I really feel strongly," Perez says, "that our neighborhood could be much more inviting, friendly and warm, maybe even healthier and safer, with more trees."

Sort of like . . . Fairmount Park.

Philly Tree People are all Tree Tenders, volunteers trained to choose the right trees for the right place and then plant and care for them. They're working with TreeVitalize, a state program dedicated to replacing the tree canopy lost to development, age, disease and negligence in hard-hit Southeastern Pennsylvania.

Mindy Maslin, manager of Tree Tenders for the Pennsylvania Horticultural Society, explains the canopy idea: "If you're standing on the street looking up, you're looking at what percentage of overall sky is blocked out by trees."

The bigger the percentage, the cooler we'll be in summer, the more storm water will be absorbed into the ground, and the nicer our neighborhoods will be.

And that's what gets Perez, Richman and Blank going - the idea that trees can raise up a neighborhood while doing good things for the local and larger environment.

Wow, are trees the answer to everything? "They make me happy," says Perez.

Not a bad start.

TreeVitalize launched in 2004, after a U.S. Forest Service study showed that the Philadelphia region had lost 8 percent of its tree cover - 34,000 acres of trees - in just 15 years.

The horticultural society got the effort off the ground in the Philadelphia area, taking it to Pittsburgh last spring. Now, it's going statewide, with a goal of one million new trees in Pennsylvania by 2012.

With help from Perez's dad, Carlos, Philly Tree People have twice mobilized dozens of friends and neighbors to plant 167 street trees in Kensington and Fishtown this year, with another 61 in the works for next spring.

In 2004, Richman bought a rowhouse, cheap, in Kensington and spent two years gutting and renovating it - and fending off thieves who ripped off tools, copper pipes, and anything else they could pry loose.

Then her boyfriend split. And the house next door exploded from a gas leak.

But Richman's tough. As an urban entomologist, she studies roaches, ants, spiders and other "pests of humans and their dwellings" for a living. What are the misdeeds of a few humans?

She kept on. "It was character-building," she says, "and now I have this nice house."

Richman also has a new boyfriend, and they made a beautiful garden where the house next door had been. This summer, they enjoyed the tropics, Kensington-style, with raised beds of elephant ears, banana trees, roses and other neat things.

Richman enrolled in Tree Tenders in 2006 "because I needed to do something, and I wanted to start meeting my neighbors, and I wanted to talk about something other than the drugs that are around our houses."

Soon, the talk turned to trees.

"In Kensington, there aren't any. It's so dreary," says Richman, 37, who grew up among Fort Lauderdale's lovely palms and mangroves.

None of those in Kensington, but with Richman and her pals, you just never know. For now, they're immersed in hornbeams and redbuds.

"The idea," Richman says, "is that we want these scumbags who don't live here, who just come to sell drugs on the corner, to see that people who live here care about their area.

"It's a small step," she adds, "but you have to start somewhere."

Two years ago, Blank and her fiance bought a rehabbed rowhouse in Kensington and began their urban adventure.

Blank, 31, works with autistic children. She grew up in West Chester with a landscaper father and a mother who was a longtime florist.

"I grew up camping and hiking in the woods. I just loved trees," says Blank, who recalls "one remarkable day" after she'd moved to the city:

"We were renting on a tree-lined block in Fishtown, and it was blazing hot. I walked home from the El, sweating like crazy, and I turned onto our block and it just was 10 degrees cooler. It looked pretty, too."

She soon joined Tree Tenders, though, like her friends, she's busy. Besides working full time, she's studying for a master's in education at Temple University and she's active in the East Kensington Neighbors Association.

Just guess what her job is there: head of the beautification committee.

Nykia Perez grew up in Kensington and in 2004 bought her own century-old rowhouse, where she has turned most of the yard into a wildlife-friendly garden.

At 32, she's director of information services at the University of Pennsylvania's Population Studies Center, but just about every spare minute is devoted to neighborhood cleanups, tree-plantings and gardening.

"If I could plant wherever I wanted," Perez says, "the whole city would be an arboretum."

Listening to her dad, a Kensington Tree Tender who works in a printing company's warehouse, you might think tree fever is hereditary. One can only hope.

"I have a vision of at least four trees on each block," says Carlos Perez.

Tender Lessons

Free Tree Tender training is available to residents of Philadelphia and Bucks, Chester, Delaware and Montgomery Counties. It involves nine hours of instruction in tree biology, identification, planting and proper care, as well as working within your neighborhood. The training is offered by the Pennsylvania Horticultural Society with the Penn State Cooperative Extension, and it's designed for people who know little - or a lot - about trees.

The next training session is scheduled for 8:30 a.m. to 1:30 p.m. Jan. 10 and 17 at the horticultural society, 100 N. 20th St. Registration is required. To register, or to find out about Tree Tender groups in your neighborhood, call 215-988-8844 or go to http://www.pennsylvaniahorticulturalsociety.org/. For information about TreeVitalize, go to www.treevitalize.net. EndText

Contact gardening writer Virginia A. Smith at 215-854-5720 or vsmith@phillynews.com.