Charles Darwin's Greenhouse and Hothouse, Down House

Emma Darwin moved into Down House on 14 September 1842 and Charles followed three days later; he lived and worked there until he died in the house on 19 April 1882. Soon after the couple arrived, a strip of the neighbouring field was turned into a kitchen garden, which came to hold an experimental plot and, later, the greenhouses. In the late 1850s, while writing On the Origin of Species, Darwin took over a corner of it for his 'experimental beds', and from 1855 to 1867 he recorded his results in an Experiment Book devoted mainly to the growth and reproduction of plants.

His study of how insects fertilise orchids, published in 1862, called for warmer growing conditions. According to Wikipedia, a new heated greenhouse built under the supervision of John Horwood, gardener to Mr Turnbull of The Rookery, was completed in February 1863; English Heritage describes a hothouse added beside the existing greenhouse in the early 1860s. Plants raised there went on to inform Insectivorous Plants, published in 1875.

In the twentieth century the house became a girls' school under Olive Willis from 1907, until 1921 according to English Heritage or 1922 according to Wikipedia. The surgeon Sir George Buckston Browne bought it in 1927 for £4,250 and opened it as a museum on 7 June 1929. English Heritage acquired the estate in 1996 with support from the Wellcome Trust and the Heritage Lottery Fund, reopened it in April 1998 and has since completed a long programme of garden restoration.

The glasshouses stand in the kitchen garden, roughly a hundred metres west-south-west of the house according to OpenStreetMap, which maps the hothouse as a building of its own. Two spaces make up the group: the greenhouse that was already there and the hothouse Darwin had built beside it in the early 1860s. English Heritage describes sloping glass roofs set to catch the sun and a boiler system that kept the air warm enough for delicate specimens.

The building answered a practical failure: Darwin had first tried to raise tropical plants in a small plant case in the drawing room, without success. One feature reveals its scientific purpose: a tunnel passageway lets bees fly in and out, essential for experiments built around pollination. This was a working glasshouse, tied to the kitchen garden and its trial beds, rather than an ornamental conservatory. Neither English Heritage nor Wikipedia gives its dimensions or says how much of the present fabric dates from Darwin's time.

Today the glasshouse holds orchids, insectivorous plants and climbers of the kinds Darwin grew at Down. Each group echoes a strand of his botanical work: orchids, whose varied flowers he showed had evolved to favour cross-pollination by insects; carnivorous plants such as sundews, which he grew for sixteen years and fed with proteins like roast beef and boiled egg; and climbing plants, which also grow on the façade and verandah of the house.

Around the glasshouse, the kitchen garden keeps the beds where Darwin experimented with two primroses, Primula vulgaris and Primula veris, and the wormstone he used to measure the activity of earthworms. Interactive panels explain these experiments in what English Heritage presents as Darwin's 'outdoor laboratory'.

Down House lies at Downe, near Orpington, on the south-eastern edge of Greater London, and is cared for by English Heritage. The glasshouse is part of the walk through the gardens, which complements a visit to the house, whose first floor has held an exhibition on Darwin's life and work since the 2009 bicentenary.

The visit continues naturally along the Sandwalk, the quarter-mile 'thinking path' Darwin followed every day, laid out on a strip of land rented from Sir John William Lubbock in 1846, and past Great House Meadow, a field of about 15 acres whose plants and insects he monitored. In season, the café uses vegetables from the kitchen garden.