Longwood Gardens, the 1,000-acre botanical garden and former du Pont estate that sprawls over meadows, woodlands, and rolling Chester County countryside in Kennett Square, has announced it is embarking on the largest makeover of grounds and buildings in its history, a $250 million project that will stretch through 2024 and transform the visitor experience.

The project, dubbed “Longwood Reimagined: A New Garden Experience,” focuses on 17 acres at the heart of Longwood and involves, among other things, construction of a new West Conservatory near the popular East and Main Conservatories.

The new conservatory will consist of a 32,000-square-foot glass house rising in a series of asymmetrical peaks and seeming to float on a shimmering pool of water. The architect is Weiss/Manfredi, with gardens and pools designed by Reed Hilderbrand.

A Bonsai courtyard along the West Conservatory and a new restaurant and private event space are also part of the plan. Other elements include construction of a new education and administration building, renewal of the Waterlily Court, and preservation of six historic Lord & Burnham glass houses from the early 20th century, to be relocated at a later date and used for year-round garden displays.

The project will require demolition of the current West Conservatory and the Cascade Garden building. The Cascade Garden itself will be moved to a more central location in a new glass house of its own. The administration building next to the West Conservatory will be rebuilt from the foundation up.

All structures are designed by Weiss/Manfredi, a New York firm perhaps best known for its design work for the Seattle Art Museum’s Olympic Sculpture Park and the Visitor Center at the Brooklyn Botanic Garden. In Philadelphia the firm’s work can be seen at the Singh Center for Nanotechnology at the University of Pennsylvania.

In a statement, the firm’s principals, Marion Weiss and Michael Manfredi, said their design for Longwood seeks to impart a series of experiences from the intimate to the grand.

“The West Conservatory, with its pleated crystalline ridge, appears to float on water and is magically reflected by day and night,” they said. “The vaults of the new restaurant and event space are carved into the hillside to reveal views of the Main Fountain Garden. A new arcade frames the historic Waterlily Court, and the great Cascade Garden is sheltered in a custom-designed glass house.”

Longwood, the former estate of Pierre S. du Pont, attracts more than 1.5 million visitors a year.

Landscape architect Douglas Reed, founder and principal of Reed Hilderbrand, said his firm sought inspiration from the designed landscape already present at Longwood. “Above all,” he said, “we believed this ambitious project must retain a sense of Longwood’s historic roots.”

Paul B. Redman, Longwood’s president and chief executive, said the transformation project has its roots in a master plan developed by Weiss/Manfredi a decade ago.

“That was a road map to get us to this point,” Redman said. “There were things that we needed to do and to put them in place, like building the experience on the east end of the garden, the expansion of the meadow, the relocation of Route 52 [completed in 2012]. The main fountain garden [refurbished in 2017] was more than just about dancing water and light and entertainment. Ninety percent of that project people don’t even see — it’s all infrastructure. And it’s not only infrastructure that supports the fountain garden, but it’s infrastructure that is setting the stage for this development, and future expansion.”

At this point, he added, “we have all of that in order and we can really start thinking about the next 100, 200 years and what that guest experience is going to be. That’s really what this is about.”

The two-year fountain garden restoration clocked in at $90 million.

The first part of the grander and more expensive project begins March 1 with restoration of the Orchid House in the Main Conservatory.

“That’s when the first fencing will go up for this project,” said Redman. “By this summer, construction fence will be up across the 17-acre site. Guests will probably be able to see earth being moved by the fall. And then we will be in construction all the way through fall of 2024. We’re anticipating that this new West Conservatory, and the new admin building and our new restaurant — everything will debut for the holiday season in 2024.”

Even when the fences are fully deployed and construction commences, Redman said, visitors will be able to venture into almost all of Longwood’s key buildings, pools, gardens, and meadows.

“They will have access to two-thirds of the conservatory spaces that they have always had access to, the main exhibition hall, the East Conservatory, all those spaces that they’ve always loved and enjoyed, and then they’re going to have access to the entire rest of the garden. This is really, truly the northwestern corner that they won’t have access to,” he said.

The $250 million price tag will be met through a combination of grants, a tax-exempt bond issue, and endowment funds.

The Longwood Foundation has given a $40 million grant toward the project, and the state has authorized a $500,000 Redevelopment Assistance Capital Program grant for expansion of Longwood’s wastewater treatment plant. The project may also draw up to $45 million from Longwood’s endowment, which stood at $826.5 million at the end of 2020. The exact size of the bond issue is being determined but will not exceed $200 million, Redman said.

He anticipates the project, once completed, will alter the visitor experience in a significant way.

“They’re going to have 17 acres of new garden to experience,” he said.

They’ll be able to eat too.

“And they won’t have to stand in line anymore to wait for food,” Redman said. “And they’re going to have access to a new garden, an experience that will be like no other place in the world. I mean, really.”