G for Glasshouse

The greenhouse – from the Roman specularium

The Roman emperor Tiberius possessed a voracious appetite for debauchery. And cucumbers. Sick and enfeebled, he was instructed by his physicians to eat a cucumber a day and, in order to guarantee supplies, he had a specularium, a house for growing plants, roofed with oiled cloth, constructed around AD 30. (The ‘cucumber’, referred to by Pliny the Elder, was probably the snake melon, a sweet fruit known today as the Armenian cucumber Cucumis melo var. flexuosus).

An alternative to oiled cloth was mica, a silicate of the mineral gypsum, which possessed a crystalline structure that allowed it to be split into thin, translucent slices. Pliny described plants being ‘placed under the protection of frames glazed with mirror stone’, one of the vernacular names for the mineral. In the winter months, fires were kept burning outside these stone walls to warm the house.

Giardini Botanici

Roman gardeners continued to improve the design of their specularia and filled them with crops of roses and grapes, although it was not until the 13th century that the Italians devised the first greenhouses that we would recognise today. These were the giardini botanici or botanical gardens (the Vatican built one of the first), structured to house new plant species being brought back to the Mediterranean countries as the empire builders explored new lands.

This glasshouse technology, together with the plants, spread initially to Holland and later to England and France in particular.

By the 15th century, the glassmakers of Murano near Venice were producing a transparent compound that found its place in what were now to be known as glasshouses or ‘conservatories’. (A conservatory referred to a building where the plants were grown in beds or borders rather than containers).

In 1599 Jules Charles, a French botanist, designed and built a greenhouse in Leiden, Holland, and used it to raise tropical plants for medicinal purposes, together with citrus fruits. The fondness and fashion for these tropical fruits led to the creation of orangeries and drove the development of ever more ingenious designs.

Great glasshouses like these, fitted with sophisticated winter heating systems, also provided the perfect venue for summer house parties for their wealthy owners. The greenhouse had become a status symbol.

(From Tales from the Tool Shed, RHS)