Climatron

The Missouri Botanical Garden, founded by Henry Shaw in 1859, already had a long tradition of glasshouses when its director, the botanist Frits W. Went, initiated an entirely new kind of conservatory. The old Palm House was demolished to make way for it. Construction began in 1959, and the Climatron opened to the public on 1 October 1960.

The St. Louis firm Murphy and Mackey were the architects, while the dome itself was designed by architect-engineer Thomas C. Howard of Synergetics, Inc. in Raleigh, a company applying the geodesic principles developed by Richard Buckminster Fuller. The garden describes it as the first geodesic dome used as a conservatory, and it is also cited as the world's first fully air-conditioned greenhouse.

It won the 1961 R. S. Reynolds Memorial Award for the architectural use of aluminium and was named in 1976 among the hundred most significant architectural achievements in United States history. Closed for renovation in 1988, it reopened in March 1990 with its original Plexiglas replaced by glass, and celebrated its fiftieth anniversary in 2010.

The Climatron is a geodesic dome 175 feet (53 m) across at the base and 70 feet (21 m) high at the centre, enclosing 1.3 million cubic feet and covering about 24,000 square feet, more than half an acre. Its frame combines aluminium tubes in compression with aluminium rods in tension and needs no interior support: there is not a single column between floor and ceiling.

The dome was originally clad in Plexiglas. During the 1988–1990 renovation this was replaced with 2,425 panes of heat-strengthened glass with a Saflex plastic interlayer and a low-emissivity coating to reduce heating costs. The climate-control system, designed to reproduce several tropical climates, keeps the temperature between 18 °C (64 °F) at night and 29 °C (85 °F) by day, with average humidity of 85 per cent. Irrigation uses tempered water purified by reverse osmosis.

The dome recreates a lowland tropical rainforest. According to the garden, it holds more than 2,800 plants of around 1,400 tropical species, including banana, cacao, coffee, orchids and the double coconut (Lodoicea), which produces the largest seed in the plant kingdom.

The landscaping combines dense foliage, rocky cliffs, waterfalls and a small hut. A river aquarium stocked with exotic fish adds an aquatic element, and a bridge offers views into the forest canopy from above.

The Climatron stands at the heart of the Missouri Botanical Garden's 79 acres in St. Louis and is included in a visit to the garden, which has two other conservatories: the Linnean House, Shaw's former orangery of 1882, and the Shoenberg Arid House. Thirty minutes to an hour is enough to circle the dome and cross the canopy bridge. Its constant humid warmth makes it a popular winter stop; at other seasons it pairs well with the Japanese and Chinese gardens, Henry Shaw's Tower Grove House and the garden's Victorian District.