Behind a state park's long wooden fence, hidden by a thick hardwood hammock, is the Florida Keys' last citrus and avocado grove, a living remnant of the island chain's agricultural past.

It has been tended off and on for 63 years, since three Key Largo pioneers positioned quarter sticks of dynamite on a cleared patch of ground and blasted evenly spaced holes in the solid coral.

The grove those men planted, along with 54.7 acres of mostly virgin land, was sold to the state of Florida in 1979 by its longtime owners, the late Herb and Donna Shaw.

The state paid $1.94 million for the land, almost all of it still preserved as hardwood hammock, and the Shaws continued to live on the property until Donna Shaw's death in 2000 at age 90.

Today, the 2.5-acre grove at John Pennekamp Coral Reef State Park is maintained as a cultural resource, according to park ranger Judy McGraw. It remains the last working Key lime grove in the Upper Keys, and perhaps all of the Florida Keys.

Tucked away down a trail where horses once trod, the subtropical forest opens to a manicured pasture, featuring rows of lime, avocado and mango trees. A lone guava tree remains.

The open pasture is a haven for hawks seeking a quick meal. One tree in the center of the grove is dotted with ripe limes as if it were an untrimmed Christmas tree decorated with small yellow ornaments.

All the trees, young and old, of different kinds, grow together in harmony, absorbing sunlight and yielding fruit each in its time. Some thicker at the trunk and older than the rest grow in uniform rows set about 50 feet apart.

Hector Clark and Hubert McKenzie, as well as former fire chief Harry Davis' father, dynamited the holes. Dirt was brought in from the surrounding hammock, and trees were planted.

Skip Shaw, the youngest son of Herb and Donna, remembers watching the men dynamite the field to create the grove.

"Dad went all over the Keys searching for big Key limes. He found a tree in Tavernier that had clusters of limes," he said. "He started two trees from cuttings and the rest were started from seed."

Peter Anderson, former assistant manager at Pennekamp in the 1970s and '80s, grew up in Key Largo and used to play checkers with Skip Shaw when they were children. Anderson, who is now manager of Highlands Hammock State Park in Sebring, Fla., recalls his unsuccessful bid as a child to pluck a ripe mango from the grove.

"I could never get a mango," he said. "Every time one got ripe, one of the workers or rangers would pick it. So I wrote my name in ink on a big one that was coming ripe, thinking they'd give me a break. A week later it was gone. I blamed the workers and rangers, but I got a surprise," he said. "Mr. Shaw said, 'Thanks for marking that mango for me. That was a good mango.'"

Anderson and former Pennekamp ranger Larry Gavagni, now retired to a 15-acre North Florida farm after his Florida Park Service career, both remember a particular hawk that would ply the pasture.

"That hawk dove on me one day," Anderson said. "I came up on him and he started to take off and came right for me."

In the last 1970s, Gavagni asked for and received then-park manager Mark Glissen's permission to restore the old fruit grove.

"It was overgrown," Gavagni recalled. "[The caretaker] who had cared for the grove and the horse stables was no longer up for the job. In fact, he died soon after I came to Pennekamp in 1975."

The grove contains six varieties of avocado, including the Stiles, named for Donna Shaw's grandfather, Frank Stiles, who supplied mango and avocado trees from his Miami farm, Gavagni said.

The last working grove is a monument to one of Key Largo's first major industries. Groves lined what is now County Road 905 in the early part of the 20th century. Boxes of limes would stack up by the road awaiting trucks that would carry them north to market.

Today, tourists swim and frolic just 100 yards through the hammock from the last lime grove. Little do they know what history grows there.

sgibbs@keysnews.com