Hothouse

History

The hothouse, or hot house, was a plant- keeping structure that provided enough heat to permit the cultivation of tropical and semi-tropical plants in temperate climates. The hothouse often formed part of a greenhouse [Figs. 1 and 2], although very often the terms were used synonymously and interchangeably with “conservatory.” Bernard M’Mahon (1806) wrote that the difference between a greenhouse and hothouse was that a greenhouse had only enough artificial heat to “keep off frost and dispel damps,” whereas the latter had an interior stove and was covered in more glass (see Conservatory, Greenhouse, and Orangery).

An area’s climactic zone determined the extent to which a heating system was necessary. Heat could be generated in several ways. Dry heating systems included charcoal fires contained in metal pots and wheelbarrows that were placed within the hothouse to give off warmth. More sophisticated hypocaust systems used cellar boilers that circulated heat through flues. This latter type, which was developed by the ancient Romans, has been found in archaeological sites in Maryland, dating as early as around 1730.1 John Evelyn, in his 1693 translation of Jean de La Quintinie, suggested caking the back wall of a hothouse with a thick layer of dry dung, fixed in place with wooden lathes. This technique, or a related one that called for manure piles to be placed under the benches, could let off heat as the manure decomposed. Perfected in the early 1820s, a wet-air or steam system circulated heated water through pipes placed underneath benches. Opening and closing these water pipes allowed the regulation of heat. This kind of system, however, was considered a luxury until the late nineteenth century. A hothouse could also be built as a lean-to glasshouse, thus benefiting from the heating system of the main house, to which it was attached [Fig. 3].

In the early to mid-nineteenth century, as fashions changed regarding the choice of certain plants, specialized hothouses were built and named accordingly. For example, the grapery or vinery, the peachery, pinery (for pineapples), palm house, rose house, camellia house, and geranium house, were built according to the specific heating and lighting requirements of each plant type.

-- Therese O'Malley