Longwood Gardens, one of North America’s most renowned botanical gardens, located outside Philadelphia in Chester County, is undergoing one of its biggest renovation projects since it was opened to the public in 1921. Longwood Reimagined: A New Garden Experience is a $250 million expansion, with 17 acres of new gardens, new restaurants, and educational spaces, and a new, 32,000-square-foot glass house called the West Conservatory. The design is being led by WEISS/MANFREDI Architecture/Landscape/Urbanism, a firm co-founded by Marion Weiss, the Graham Professor of Practice in Architecture at the Weitzman School of Design.
Weiss/Manfredi is known for prominent public, cultural, and educational buildings including the Seattle Art Museum Olympic Sculpture Park, the visitor center and overlook at the Brooklyn Botanic Garden, the Tsai Center for Innovative Thinking at Yale, and the new US Embassy in New Delhi, currently under construction. Next year will see the publication a of new book by Weiss and her co-founder, Michael Manfredi, titled Drifting Symmetries, documenting their holistic design approach, which prioritizes connections between landscapes, sites, and buildings. In an interview, Weiss recently spoke about the ongoing work at Longwood Gardens. The conversation has been edited for length and clarity.
How did you win the Longwood Gardens commission?
Just over ten years ago, we were part of a team with West 8 to develop a master plan that would establish a framework for Longwood’s evolution. Since then, Longwood has continued working with WEISS/MANFREDI as lead designer, in collaboration with Reed Hilderbrand, on Longwood Reimagined, which extends Longwood’s distinguished history of commissioning and collecting outstanding garden designs and glasshouses.
The reimagination of the west side of Longwood Gardens extends west from the ridge line where Pierre du Pont built the first conservatory structures. The project presented an opportunity to repurpose and relocate a collection of smaller production greenhouses and remove a parking lot to create a new site along the ridge for a new conservatory and a collection of new and rejuvenated gardens. It also enabled Longwood to support their audience and their mission with additional buildings including an education and administration building, a new restaurant and event space, a rejuvenation of the Sir Peter Shepheard Waterlily Court, and, especially exciting, the relocation and reconstruction of the Roberto Burle Marx garden, giving his only extant garden in North America pride of place.
There is a big design legacy there, particularly in landscape architecture. You mentioned Peter Shepheard, who served as dean of what is now the Weitzman School at Penn, and Burle Marx and Isabelle Green, and others. What is it like to wade into a space with all that cultural baggage?
It is super interesting. For us, Longwood Gardens as a client has been a dream come true. Our practice, which is called WEISS/MANFREDI Architecture/Landscape/Urbanism, is committed to weaving all these disciplinary strands together to create places of enduring beauty and meaning. We brought Reed Hilderbrand onto our team, who brings unique horticultural brilliance to the project which is especially evident in the Mediterranean garden inside the conservatory and formal tree allées layered into the conservatory complex. Water occupies almost half the footprint of the West Conservatory. As pools wander inside and outside, the conservatory appears to be floating on water, creating an incredibly magical place that is, literally, a world apart.
With the new West Conservatory, we’re taking the legacy of the glass house, which is so central to Longwood’s identity, and projecting it into our contemporary moment in time with comprehensive sustainable systems. The building’s pleated roof collects water that is held in detention tanks for reuse, the ventilated roof and façade are activated to support natural displacement-air ventilation, and 10 earth ducts that encompass 1,200 linear feet draw air through the earth to further condition the space. With the earth holding a steady 55 degrees, these earth ducts naturally pre-heat or pre-cool the space depending on the season, and a series of deployable shades further support summer cooling or winter thermal insulation. Unlike glass in a typical building, with high performance coatings, this conservatory has super clear, low-iron glass that enables the plants to thrive. And, important to a glass structure with plants inside, the delicate frit on the glass is designed to guide birds away from the glass. At 32,000 square feet, it will be the largest free-standing living, breathing, glass house in North America.
It also interesting to think about the cultivated garden inside the glass house during this era of intense climate change. The interior Mediterranean garden and aquatic plants remind us that, as our world becomes hotter and wetter, these display gardens may in fact be the very gardens that will thrive in the future.
“Inhabiting the topography has enabled both worlds, the constructed and the natural, not to be in conflict with each other but rather experienced as part of a continuum.”
Can you talk about the formal legacy of the glass house, and the design style of the buildings at Longwood generally?
The evolution of the glass house, from the early 16th century forcing houses to the 19th century inventions of Paxton, all informed the legacy of invention that has underpinned Pierre du Pont’s early conservatories at Longwood Gardens, and also the transcendent main fountain garden that he designed and engineered. The early conservatories at Longwood are interesting hybrids that are simultaneously robust architecture and light-filled conservatories. For the West Conservatory, we designed an asymmetrically pleated glass house, supported by a grove of columns that arc, like the tree branches of the nearby sycamore grove, to enable very large spans that are unconventionally delicate. This expression would not have been possible with more traditional post-and-beam construction that informed the earlier buildings.
Our design also reflects our preoccupation with movement and altering views through the conservatory with perspectival convergence. The pleating geometries of the glass ridges align with the height of the historic east conservatory, while the tapered geometries create theatrical perspectives of the gardens, and the catenary dipping of the long north and south elevations create both expansive and intimate places to experience the garden inside.
Longwood has been trying to bring the Brandywine Valley landscape into the property a little bit more. Was there some attempt to bring that into the building design too?
Absolutely, yes. We were inspired to bring the relaxed geometries of the Brandywine Valley landscape into the crystalline geometries of the west conservatory. We were also interested in recasting the ridgeline that situates all of Longwood's conservatories into a truly crystalline ridge, opening to views of the adjacent Abondi Fields and Brandywine Valley beyond. The 17-acre transformation includes a tapestry of meadows and wild grasses that weave into the formal gardens, intersecting in beautiful tension with each other at a grove of 100-year-old sycamore trees.
What did you learn from doing the project at Brooklyn Botanic Garden?
Our visitor center at the Brooklyn Botanic Garden is something that from the city’s edge, appears to be 100 percent architecture, and 400 feet later as you make your way into the gardens, it’s 100 percent landscape. It is those chameleon moves that are inevitable and natural but in fact are incredibly unusual. Through creating a wandering hybrid of architecture and landscape, we were able to choreograph a slow journey to leaving the city behind, arriving in the garden to discover a place that is always changing over time.
At Longwood, we were challenged to find a site for both a new restaurant and event space. We wondered, as we did with the visitor center and the Brooklyn Botanic Garden, if it would be possible to create a new building that could hide in plain sight. Rather than adding two new freestanding buildings, we chose to excavate 22 vaults behind the existing 400-foot-long, 20-foot-high existing retaining wall that formed the plinth of the historic conservatory. By carving through the wall and earth with a series of vaults, we were able to create both a restaurant and event space. This is a case where capturing space within the earth, rather than building new structures, will create a collection of both intimate spaces with expansive views of the Main Fountain Garden. With both projects, inhabiting the topography has enabled both worlds, the constructed and the natural, not to be in conflict with each other but rather experienced as part of a continuum.
“The interior Mediterranean garden and aquatic plants remind us that, as our world becomes hotter and wetter, these display gardens may in fact be the very gardens that will thrive in the future.”
How does this project connect to your teaching at Penn?
I teach the final semester research studio of the three-year Master of Architecture program. My studio includes both architecture and landscape architecture students interested in transdisciplinary projects that are located within the tapestry of architectural, landscape, infrastructural and ecological concerns. My studio explores opportunities to create new public realms that leverage both natural and man-made forces, finding new reciprocities between infrastructure, nature, and urban life. Rather than imposing architecture on the landscape, it is the productive intertwining that enables us to address pressing contemporary challenges.
One exciting aspect of teaching at Penn is that Weitzman encompasses, under one umbrella, landscape, architecture, preservation, art, urban design, and city planning. I chose to teach at Penn because those disciplines were viewed as intrinsically relevant to each other. The legacy of people like Ian McHarg, Kahn, Venturi, and Giurgola underpin the enduring value of both natural systems and the tactile presence of constructed form. Yet today, those foundations have expanded to include increasingly cross-disciplinary modes not just form finding, but problem finding.
What is the timeline for finishing and what else do you want to say about the design process?
The project is going to open exactly a year from now. It will be the most ambitious realization in a century of America’s greatest center for horticulture displays. Across 17 acres, it’s really going to offer a newly unified but consistently varied journey of indoor and outdoor gardens, with vistas over Pennsylvania’s Brandywine Valley. And while Longwood Gardens is committed to cultivating new forms of natural beauty, for us, its legacy of invention and innovation resonates profoundly with our ambition to discover new ways for architecture and landscape to support each other.
We were just there earlier this week and it is so exciting to see it actively coming to life. While master plans often remain exactly that, this is a project that has evolved over time, finally coming into focus to feels as if it should have always been this way. As we reflect back on more than a decade of planning and design, the through-line has been the far-sighted vision of Longwood.
As we think about the times we live in just now, when our public and natural worlds are increasingly fragile, we hope Longwood Reimagined will become not just a place of natural beauty, but also a place of respite and inspiration.