Seventeen thousand trees planted, thousands more to go, Louis Cantafio tallied while handing out tools at the Franklin Parker Preserve near Chatsworth.

"When you unload 25,000 trees on 14 square miles, you think, 'Oh my God, I'll never get this done,' " said Cantafio, senior land steward of the New Jersey Conservation Foundation.

But thanks to volunteers from groups including the New Jersey Youth Corps in Camden, and Rutgers and Kean Universities, the preserve's former cranberry bogs off Route 563 in Burlington County are getting a boost in reverting to their natural swampy state.

The massive planting of tree seedlings, which is expected to conclude tomorrow, stems from a U.S. Department of Agriculture grant worth $5.4 million that helped the foundation create the 9,400-acre preserve - the largest private conservation deal in state history. Wetlands restoration was a condition of that 2005 grant.

With access still limited four years after its purchase for $12 million, the land is nearly as mysterious to the public now as when prominent farmer J. Garfield DeMarco owned it. But scientists are excited about their discoveries, especially in areas untouched since the 1930s.

"It's as exciting as exploring a new planet," said Emile DeVito, the foundation's science and stewardship manager. "The more we look, the more we find. You wonder: How can that be happening in New Jersey?"

The Brooklyn Botanic Garden has discovered more than 40 rare plants at Parker. State biologists have been banding bald eagles and monitoring rare snakes and amphibians. A joint survey by the American Entomological Society and the Academy of Natural Sciences in Philadelphia has observed a half-dozen insects never before recorded in New Jersey, including, they think, a new species of crane fly.

"It's not hands-off nature," said John Galehaus, assistant curator for entomology at the Academy. Temple University and Richard Stockton College students are amassing valuable field experience, he said.

In addition to bogs, the preserve consists of reservoirs, wetlands, upland forest and Atlantic white cedar swamp. Franklin Parker, its namesake, the first chairman of Pinelands Commission and a founder of the conservation foundation, died in February.

The entire property is open to the public by canoe and by foot, bicycle, and horseback, though trails are few. Hunting is allowed by permit. The conservation foundation, the Ocean County parks department, the Willingboro Astronomy Club, and the Pinelands Preservation Alliance conduct periodic classes there.

"Anyone who's adventurous can walk in and check it out," said Sandy Perry, the foundation's communications manager.

But visitors are often confused by the "access by permission only" signs still scattered along the property's 70 miles of frontage roads, Cantafio said, a remnant of the foundation's first year of ownership, when the property was open only to scientists.

There is no parking lot, visitor's kiosk, or even a detailed map yet.

"We really want to make it more visitor-friendly," Perry said. "There are regulars who visit already, especially birders. They love the bluebird trail created by one of our volunteers."

Plans include marked nature trails, footbridges and viewing platforms atop existing irrigation huts. But that may require more money.

The foundation is short of staff and depends heavily on volunteers, said Chris Jage, its assistant director for South Jersey.

"This property transformed our organization," he said. A four-member stewardship staff now manages 20,000 acres statewide, half of them at the Parker Preserve.

"The wetlands restoration is more expensive and more complicated than anything we've ever done," he said.

The bog restoration project started last fall when 80 acres of compacted agricultural soil were bulldozed to form hummocks and pools that encourage plant diversity. In the next phase, manmade dikes and irrigation canals over nearly 1,000 acres will be removed, allowing the water table to fluctuate naturally.

Volunteer planters were delighted recently to find endangered humped bladderworts, a floating, yellow, insect-eating flower, growing in the bulldozed area.

Pinelands Nursery in Columbus germinated the seedling trees from Atlantic White cedar seeds collected from the preserve's mature trees. The cedars were once abundant in New Jersey, but since colonial times, 80 percent of the species has been harvested for shipbuilding and construction because of its natural resistance to rot and insects.

"If one-tenth of mine grow, I'll be happy," Nels Anderson of Indian Mills said after planting a tray of seedlings. Anderson also built and monitors the preserve's 55 bluebird boxes, which yielded more than 100 baby birds over the summer.

Although the state owns 40 percent of the preserve, the foundation retains decision-making power.

"Having a nonprofit in charge is critical," said Carlton Montgomery, longtime director of the Pinelands Preservation Alliance, a watchdog group.

Preservation hasn't been hamstrung by state budget woes or political battles, he said, but better public access would build support for the foundation's efforts.

"The more who can enjoy the land responsibly, the more people will share the goal of preserving it," he said.

Frequent volunteer Michael Hogan of Dorothy, Atlantic County, worries about unfettered public access.

"There are real special places there that people don't need to be," Hogan said. A photographer and amateur botanist, he has discovered orchids and other rare plants he hasn't seen in the Pine Barrens since he was a child. "It's an amazing place."

Contact staff writer Cynthia Henry at 856-779-3970 or chenry@phillynews.com.