Since it was built in 1999, the Children's Garden has not had a lease, license, or agreement to use the land, Treasury spokesman Bill Quinn said.
The state provided annual grants until 2010 to help cover operating costs, Quinn said.
According to a 1999 Inquirer article, the Children's Garden was developed by the nonprofit Cooper's Ferry Development Corp. in conjunction with the then-state-owned New Jersey State Aquarium and Camden City Garden Club Inc.
The club still operates the garden. Quinn could not say how it initially got access to the land.
The state has tried for at least two years to reduce the footprint of the Children's Garden and charge rent for office space, Devlin and Quinn said Thursday.
Devlin refused, he said, citing the group's nonprofit status and 1999 designation as the parcel's "developer operator." The garden hosts at least 100,000 visitors a year, he said.
"It's not like we can go someplace else. . . . This garden isn't on wheels," said Devlin, who plans to enlist the community to help him fight the state.
The Children's Garden began as a "horticultural playground" but has expanded its mission to include on- and off-site nutrition and environmental, science, and math programs. It has a butterfly house, dinosaur garden, and carousel, and is headquarters of the club.
The club has overseen development of more than 100 community gardens in the city. It was celebrated in Michelle Obama's 2012 book, American Grown: The Story of the White House Kitchen Garden and Gardens Across America, which featured photos of Camden youths tending crops.
Whole Foods last year began a two-year partnership with the Children's Garden to develop community gardens and nutrition-related projects.
Herschend, the aquarium owner-operator, pays Camden 50 cents per patron in lieu of taxes, an arrangement critics have said shortchanges the city. Quinn said terms of the land transfer to Herschend had not been resolved.
"We have no specific plans to expand at this time," aquarium spokeswoman Kim Walker said Thursday. But Quinn said Herschend had proposed "substantial investments," including building attractions at the site that would be beneficial to the city.
Camden Mayor Dana L. Redd could not be reached for comment Thursday afternoon.
Earlier in the day, Redd hosted a ceremony at Adventure Aquarium to launch the Camden Collaborative Initiative, a public-private partnership intended to identify funding sources for environmental projects such as brownfield site cleanups, storm water management, and upgrading the city's antiquated sewer system.
Redd touted the success of the Camden SMART program, started in 2011 to address frequent severe flooding in the city due to Camden's combined sewer/storm water system. Much of that success is due to rain gardens created to catch prevent water runoff.
The city was awarded a Sustainable New Jersey bronze certification last year for its green efforts.
The garden club helped Camden attain that certification, said Devlin, who called the planned land transfer a "theft from the Camden City Garden Club and the city."
"We have over 10,000 Camden kids come here free of charge each year. . . . It's a safe haven and safe recreation," he said.
Contact Claudia Vargas at 856-779-3917, firstname.lastname@example.org, or follow on Twitter @InqCVargas. Read her blog, "Camden Flow," at www.philly.com/camden_flow .