Tropical Plant Greenhouse (熱帯植物園温室), Honai Park

On 11 April 2023 the city of Sanjo announced the renovation of the tropical greenhouse and of the adjoining children's play area: part of the planting was renewed, the tiles were replaced, and a photo corner was installed, with a giant banana-shaped bench. The park's own website describes the building as steel-framed, single-storey in one part and two-storey in another.

The notices on the park website concern footpaths partly closed after a landslide and the presence of bears in the park, and they carry no precise dates.

The park's website describes the greenhouse as a steel-framed building, single-storey in part and two-storey in part, with a total floor area of 878.5 m². The city's 2023 release gives 879 m² and calls the building entirely glazed, a point a regional tourism portal repeats.

Photographs published on the park website under the caption 温室通路 (greenhouse passage) show a metal framework carrying a grid of thin glazing bars, transparent panels and vents in the upper section. A visitor comment from 2016 describes a plastic "vinyl house" (ビニールハウス), a description that neither the photographs nor the official texts support.

A regional portal gives a height of 15 m, but the municipal page applies that figure to the tallest plants, not to the building.

The park's website, the prefectural listing and the city all give a figure of about 500 subtropical species. The municipal release of 2023 mentions plants from South America and South-East Asia and notes that flowers and fruit can be seen throughout the year.

The park's website names a phoenix palm (フェニックスヤシ), banana, hibiscus, calliandra (カリアンドラ), allamanda (アラマンダ), aristolochia (アリストロキア), トックリキワタ and サンゴバナ, with the Japanese names kept as printed on that page. The published photographs show dense beds, a path of stepping stones and climbing plants trained over a metal arch.

A regional portal gives a different count, 130 species and 1,800 plants, which no other source repeats. Because the 2023 renovation renewed part of the planting, the list published by the park may no longer be exact.

The greenhouse sits within Honai Park, an area of 88,305 m² in Sanjo. The park also lists a plant advice office (緑の相談所, a two-storey reinforced-concrete building of 553 m²), a café, a lecture room and an exhibition hall, and a tea room that the park website says is heated and air-conditioned. A fountain with random jets, which the website presents as the best in the prefecture, completes the grounds.

The city's 2023 release links the park with the roadside station Michi-no-Eki Teien no Sato Hona (道の駅 庭園の郷 保内) and announced a spring park festival for 28 May 2023. According to the prefectural listing, the plants can be seen all year, so the greenhouse is worth a visit in any season, combined with the outdoor paths of the park.