Tanghuawu Greenhouse, Zhongshan Park (唐花坞)

Zhongshan Park occupies the former Altar of Land and Grain (Shejitan) of the Ming and Qing dynasties. Opened to the public in 1914 at the instigation of Zhu Qiqian, it acquired, so that flowers could be shown in every season, a greenhouse that the sources date to 1915, one of them placing the work between the winter of 1914 and early 1915. Built of brick and timber west of the altar's south gate, in what was then called Central Park, it had fourteen rooms arranged like the outspread wings of a swallow, one of them under a roof of five-coloured glass. It was also known simply as the warm room.

The name refers to an old craft: the character tang stands in for a word meaning to heat with fire, and 'tang flowers' are flowers forced into bloom. The Tang-dynasty miscellany Youyang zazu, by Duan Chengshi, already describes peonies brought into flower in midwinter in earthen kilns heated from all sides. In Beijing the practice spread from the Yuan dynasty onwards, notably around Caoqiao in Fengtai, and under the Qing forced flowers were exchanged as New Year gifts.

In 1936 the greenhouse was rebuilt on the same site in reinforced concrete and given electric lighting and heating, becoming Beijing's earliest modern greenhouse; it is still in use. From the 1950s the park's gardeners studied forcing systematically, and by the 1980s they had developed a well-rounded method for controlling flowering times. They helped draft a Beijing local standard on delaying the flowering of spring-blooming woody plants, issued in December 2020. The park celebrated the greenhouse's 110th anniversary in 2025.

The present building is the one rebuilt in 1936. It has a reinforced-concrete structure, eaves covered with glazed tiles and a glass roof. Its plan, described as swallow-winged, keeps the outline of the first building, but the central section now takes the form of a double-eaved octagonal pavilion.

The name itself sums up the purpose: the first character refers to heating and the last, wu, to a building beside water, so the whole can be rendered as 'waterside flower greenhouse'. The greenhouse stands in the south-western part of the park, east of the Eight-Pillar Lanting Pavilion.

The means of heating have changed over time. According to the head of the park's horticultural technology section, earlier generations raised the temperature with fermenting manure or by burning wood and coal; natural gas and electricity now make every stage controllable and measurable, so that flowering can be timed more precisely. The sources consulted name neither the designer of the 1936 building nor its floor area.

The Tanghuawu serves as a flower exhibition hall all year round, so something is in bloom whatever the season. Its speciality remains forcing: the park's gardeners can set the flowering time of more than twenty kinds of plants, among them lilac, magnolia, forsythia and wisteria, using temperature, pruning and applied hormones to bring blooms forward or hold them back.

Major shows punctuate the year. For the 2025 Spring Festival, the exhibition 'Tanghua Chuanyun, Chunnuan Huawu' brought together more than 150 pots of some twenty kinds of forced flowers alongside more than a thousand pots of festive plants, among them azaleas, dendrobiums, moth orchids, wintersweet and forsythia. In spring 2025 the greenhouse hosted an exhibition marking thirty years of tulip displays in the park, with more than sixty varieties of tulips and other bulbs and nearly ten thousand plants. In March 2021 the Huifang Garden, whose visit is paired with that of the greenhouse, was showing wintersweet in flower and an orchid display.

The Tanghuawu stands in the south-western corner of Zhongshan Park, which covers 23 hectares, east of the Eight-Pillar Lanting Pavilion. Half an hour is enough for the greenhouse, a little longer if the Huifang Garden, whose visit is paired with it, is added. The two high points are the Spring Festival, when forcing brings spring flowers into bloom in the depths of winter, and spring itself, when the park shows its tulips, a tradition now some thirty years old. Several hundred thousand people step inside the greenhouse every year.