Hiroshima Botanical Garden Large Greenhouse (広島市植物公園 大温室)

Hiroshima Botanical Garden (広島市植物公園) owes its existence to a decision of the city council, which approved its creation in July 1972. It opened on 3 November 1976 as a municipal facility, though outside the city limits: the chosen site then lay in Itsukaichi, a neighbouring town in Saeki District. The 1985 merger brought Itsukaichi into Hiroshima, and the garden has since been part of Saeki Ward. It covers 18.3 hectares and is managed by a municipal foundation devoted to green spaces and living things (広島市みどり生きもの協会).

The large greenhouse, the garden's emblem and one of its main facilities, was renovated more than forty years after the opening and reopened on 3 March 2018. A visit report published shortly afterwards in a Japanese technical journal (J. IEIE Jpn.) notes that the exterior was left unchanged: the works focused on the route through the interior, with the addition of a raised walkway.

To accompany the transformation, the garden brought in an Australian baobab in October 2017 from Kununurra, Western Australia, some 11,000 km away. The same report relates that the tree had survived a bushfire in its native habitat: part of the trunk is still blackened, although the mark is hard to notice without being told. Other improvements came with the renovation, such as doubling the area planted with irises in the Japanese garden and enlarging the rock garden.

The large greenhouse is an all-glass volume 35 metres wide, 62 metres deep and 21 metres high, which places it among the largest in the Chūgoku-Shikoku region. Its outward appearance was not altered in the 2018 renovation; the work mainly changed the way visitors move through the interior.

A raised walkway, set about 2 metres above the ground, now crosses the greenhouse. Barrier-free, it adds a second level to the visit: crowns, foliage and flowers can be seen from above, which the 2018 report describes as the main novelty of the works.

The space is organised into three sections: a tropical waterside corner (水辺のコーナー), a jungle corner (ジャングルコーナー) and a corner devoted to fruit and plants of everyday life (くだものと暮らしのコーナー). The sources consulted name neither the architect of the original greenhouse nor the designers of its renovation.

The greenhouse displays some 700 varieties of tropical and subtropical plants, about 5,000 specimens in all, arranged to evoke their natural habitats. Its emblem tree is an Australian baobab (オーストラリアバオバブ) planted in 2017, whose trunk is about 2 metres across; the 2018 report presents it as the largest specimen in the country.

Plants given prominence include cacao, dragon fruit, black pepper and banana, along with hibiscus and Cattleya orchids. The jungle and waterside sections recreate the atmosphere of humid tropical forests.

Beyond the large greenhouse, the garden has glasshouses devoted to cacti and begonias, as well as tropical water-lily pools. It grows some 11,650 species and varieties in total, and around 150 kinds of hydrangea (1,300 plants) bloom in its woodland area during the rainy season.

The large greenhouse is the flagship building of an 18.3-hectare garden in Saeki Ward, west of central Hiroshima. An hour is enough to walk through it at ground level and then along the raised walkway; more time is needed for the cactus and begonia houses and the tropical water-lily pools. The irises of the Japanese garden flower in May and June, followed by the hydrangeas of the woodland area during the rainy season. Being covered, the greenhouse also makes for a visit in bad weather, whatever the season.