Maggie Knapp is about as lean and fit as a 50-year-old woman can be. And no wonder: She's spent literally half her life working outdoors at Jenkins Arboretum in Devon, where she's the head gardener.

"Working outdoors" sounds as if she's leisurely raking leaves. Knapp does that, yes, but she also splits wood, chases trespassing deer, mans the snow plow and wields a steady chain saw. She prunes, plants, propagates, and weeds - and hauls a yeoman's load of mulch.

You can't miss her. Spend even an hour at this 46-acre public garden, and she'll whiz by you in a golf cart, troubleshooting and problem-solving along 1.2 miles of paved walkways. You'll also find her doing walkabouts with visitors, training volunteers in the greenhouse, or, inside the John J. Willaman Education Center, sitting cross-legged on a quilt reading nature stories to kids.

"My mom does the job of 10 men. She's pretty much my Superwoman," says Samantha Knapp, 25, a senior at Savannah College of Art and Design in Georgia and the elder of Maggie and Jeffrey Knapp's two daughters.

Younger daughter Madelyn is 22, a 2011 Duquesne University grad and promotions assistant at B101-FM radio. She just applied for a marketing job at Phipps Conservatory and Botanical Gardens in Pittsburgh. "So maybe the apple won't fall too far from the tree," she says.

When their parents moved into the Browning House at Jenkins in 1986 - Jeff, a onetime landscaper, was the first to be hired, followed by Maggie - the arboretum was a relative youngster, too. It only opened to the public in 1976.

As the Knapp family grew - and grew up - so did Jenkins. It now has maybe 30,000 visitors a year, though it's hard to know. The arboretum is open 365 days a year with free admission, so people come and go.

The Knapps had never heard of the place until shortly before Jeff's job interview. "Jenkins was off the radar screen, not ready for prime time," he says.

For years after that, it was considered "a hidden gem" in the region's glittering array of public gardens. "A lot of locals still don't know it's here," says Jeff, 54, now creative director for a Bucks County communications firm and the arboretum's longest-serving volunteer.

But it's not a secret anymore. And while, as Jeff says, "it's not Longwood Gardens and it's not Morris Arboretum," Jenkins is a special place.

"Once you see and know it, you'll never have a reason to go anywhere else," says Maggie, who grew up on 30 acres in rural Downingtown, the youngest of Madelyn and Bill Hart's six children. Bill, who died in 1998, was a well-known broadcaster on WCAU-TV and radio.

Being the child of a public figure who was constantly required to be "on," Maggie says, instilled in her a deep desire for privacy and authenticity in her own life. Growing up in the woods - "that was my playground" - taught her to love nature.

"I knew, someday, I would work outside," she says.

The road to Jenkins had a few pit stops, however. Maggie worked in a box factory till the glue made her sick. She picked cookies off the oven belt at Pepperidge Farm - and hasn't had a cookie since.

Through a friend, she met Jeff, whom she still calls "the love of my life." They've been married 26 years, most of it spent in this idyllic place.

"It was a perfect fit," says Jeff.

Not always, says Samantha, known as Sam, who recalls feeling like an outcast among friends living in traditional suburban developments. "Their neighborhoods had kind of a honeycomb feel, all the kids together," she says.

But as she got older, she realized "just how crazy special the arboretum was, and whenever I had friends over, they'd say, 'Oh my God! This is such a cool place.' "

Sam loved to sit down by the pond with her colored pencils, drawing day lilies, her favorite flower. And sledding was amazing. Time it right, and the trip could last 60 seconds, all the way from the top of the hill to the creek at the bottom.

Madelyn has a favorite memory, too - of the old garage/workshop that was torn down for the new education center. "I would sit on a stool in the corner and breathe deeply . . . the smell from cut grass and grease from the mowers and the old antique tools hanging on the walls.

"It's my favorite smell in the world, probably because it makes me think of my mom," she says.

Mom, known as "Mags" to one and all, shared every inch of "the arby," as she calls Jenkins, with her husband and daughters.

Together they fret over drought, early frost, and aphids. They once rescued a baby duck whose family had been wiped out by predators and nursed a crow that fell out of its nest. They watch in awe as red foxes race around the pond and note how, in their quarter-century here, everything has grown and filled in.

Always, the plants come first.

"I identify with plants. They can't fake it. They are a life and they matter," says Maggie, who graduated from the Barnes Foundation's horticulture program in 1999.

Jenkins executive director Harold Sweetman is traveling in South America and could not be reached. But development director Janet Bauman says of Maggie: "She has a warm heart. She loves each and every plant as if they were her children."

"She's fearless, a real pistol, a happy pistol," adds John Haas, a 10-year arboretum volunteer who laughs at the many "Maggie-isms" that keep everyone entertained. For example, to "girlie up" means to dress up, "get schnazzy," as opposed to looking like a "schlump-a-dink."

But Jeff acknowledges that, with the girls grown, he and Maggie are "very close to our next chapter. And we're not getting any younger," he says.

For now, it's winter, a season that brings its own joy and beauty - and more hard, honest work. That is still welcome.

As Maggie says, "I'm planted here."

Watch Maggie Knapp talk about a Franklinia tree by the pond at Jenkins Arboretum at www.philly. com/ginnyEndText

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