Longwood Gardens Conservatory

Longwood's glasshouse history begins in 1914, when the industrialist Pierre S. du Pont (1870–1954) added an L-shaped conservatory to the old Peirce farmhouse, doubling its size. By 1916 he was contemplating indoor facilities on a far grander scale. Work on the great conservatory began in 1919, the year the Camellia House was also built, and it opened to the public in 1921.

In the winter of 1920, on a trip to Santa Barbara, du Pont bought mature citrus trees, tangerines, grapefruit and oranges, to plant the Orangery. A Music Room followed in 1923. In 1928 the architect E. William Martin designed an addition first known as the Azalea House, and in 1929 the Ballroom built to house an Aeolian organ of 10,010 pipes, described as the largest ever installed in a private residence. The organist Firmin Swinnen played there most Sunday afternoons until 1956. The organ was restored between 2004 and January 2011.

Later decades brought a string of additions: the Palm House (1966), Isabelle Greene's Silver Garden (1989), Roberto Burle Marx's Cascade Garden (1992), the Mediterranean Garden (1993), the restoration of the East Conservatory under Sir Peter Shepheard (2005–2006), the Children's Garden (2007) and Kim Wilkie's Green Wall (2010). Launched in 2021, Longwood Reimagined, the most ambitious transformation of the conservatory in a century, opened in November 2024.

The historic conservatory unfolds as a series of rooms. In the Orangery, citrus trees stand between columns clad in creeping fig (Ficus pumila) that still grows there. The Exhibition Hall has a sunken marble floor that can be flooded with a few inches of water to create a mirror. The East Conservatory covers half an acre (about 2,700 m²) under a vast ridge-and-furrow roof echoing the Orangery's, with a central stream, a 16-foot-wide waterfall and three heated, black-dyed pools.

The West Conservatory, designed by WEISS/MANFREDI with landscape architects Reed Hilderbrand, covers 32,000 square feet (about 3,000 m²). Its asymmetrical peaked roof reinterprets historic Lord & Burnham glasshouses, and its arching steel columns and beams evoke branches. It has 1,958 engineered glass panels with reflective dots for bird safety, earth-duct ventilation, computer-controlled vents and shades, and underground tanks collecting rainwater from more than an acre of roofs. Longwood describes the whole as a four-acre conservatory.

The conservatory holds more than 13,500 plant taxa, including over 4,500 orchids of 2,500 taxa, displayed on custom trellises in the Orchid House. The main conservatory combines mature trees, meticulously grown hanging baskets and bird-of-paradise, with displays that change with the seasons; the Exhibition Hall still has bougainvillea planted in the 1920s.

The East Conservatory features Mediterranean and subtropical flora: citrus, camellias blooming from October to March, azaleas, hanging ferns and palms. The West Conservatory gathers more than 60 permanent species from Mediterranean climates (acacias, bay laurels, cypress, Leucospermum, Leucadendron). The Cascade Garden, Burle Marx's only design in North America, now occupies its own 3,800-square-foot glasshouse, and the Waterlily Court shows tropical waterlilies and Victoria water-platters.

The conservatory forms the heart of the Conservatory District on the 1,077-acre estate at Kennett Square. Allow at least two hours to take in the historic rooms, the East and West Conservatories, the Orchid House and the Children's Garden. The historic rooms host the Chrysanthemum Festival each autumn, and the displays change with the seasons. The visit can be combined with the Bonsai Courtyard, the Waterlily Court and the estate's outdoor gardens.