Longwood Gardens West Conservatory

The West Conservatory is the centrepiece of Longwood Reimagined, the programme Longwood Gardens launched in 2021 to rethink 17 acres of its conservatory and surrounding grounds. The garden describes it as the most ambitious transformation of its glasshouse complex in a century, that is, since industrialist Pierre S. du Pont opened the original conservatory in 1921, after construction began in 1919.

To make room for the new building, two older spaces, the Mediterranean Garden and the Palm House, closed in 2021 and were removed. The conservatory was designed by the New York practice WEISS/MANFREDI, the interior gardens and pools by landscape architects Reed Hilderbrand, with Bancroft Construction as construction manager. The wider project also produced a 3,800-square-foot glasshouse for the relocated Cascade Garden, the only North American garden by Roberto Burle Marx, as well as a Bonsai Courtyard, a renewed Waterlily Court, an enlarged Orchid House under a new glass roof, a restaurant and a learning hub called The Grove.

The whole complex officially opened on 22 November 2024. The overall transformation has been reported at around $250 million.

The building encloses 32,000 square feet (about 3,000 m²) of glass and steel. Its roofline of asymmetrical peaks takes its cue from historic Lord & Burnham greenhouses while also recalling the rolling hills of the Brandywine Valley. It is carried on a sequence of curved, non-repeating steel moment frames whose arching columns and beams echo the loose geometry of tree branches.

The glazing consists of 1,958 engineered glass panels printed with reflective dots to reduce bird strikes. The conservatory rises from a rectangular pool that reflects it, so that the whole structure appears to float. Climate control favours passive means: computer-controlled windows, roof vents and shutters for natural ventilation, automated shading, thermal blankets, earth ducts and a geothermal heat pump. Underground tanks collect rainwater from more than an acre of roofs for reuse. The architects speak of climate-activated walls and roofs that open and close as the seasons turn.

The interior gardens are laid out as planted islands on the water, linked by bridges and edged with canals and low fountains. They hold more than 60 permanent species from the world's Mediterranean-climate regions: the Mediterranean Basin, South Africa, Chile, Australia and coastal California. Among them are acacias, bay laurels, cypresses, aloes, blueblossom (Ceanothus), Greek horehound and southern African proteas of the genera Leucospermum and Leucadendron. Century-old olive trees give the planting its structure. The islands are replanted seasonally, so the composition shifts through the year around this permanent framework.

The West Conservatory extends the 1921 conservatory to the west and forms part of a route under glass that leads, depending on the path taken, to Burle Marx's Cascade Garden, the Orchid House and the Bonsai Courtyard. Its dry, bright atmosphere contrasts with the tropical rooms nearby and makes it especially welcome in winter. Allow several hours for the conservatory and the outdoor gardens, notably the Main Fountain Garden and the Waterlily Court, whose water lilies peak in summer.