It is native of China, Korea and Burma, with lavender-blue, bluish-violet, purple-blue, blue-lilac or sky blue flowers.

[excessive citations] It has a thick,[2][3][4] (the size of a man's thumb),[5] creeping,[5][6] buff (coloured),[7] or greenish rhizome.

[12][5] It has a 1 cm long pedicel (flower stalk),[12] which is shorter than the spathe,[5] but similar in size to the ovary.

[6] The stems (and the branches) hold between 1 and 3 flowers,[31][26][32] in late spring,[14][17][28] or early summer,[2][17][20] between April and May,[26][33][34] or June.

[9] mottling,[2][18][25] veining,[8][23][39] streaks,[6][9] or spots,[2][10][4][24] around a toothed or lacinated (fringed),[7][5] white crest.

[39][36][38] They have a bi-coloured claw (part of the petal closest to the stem), white and violet or lilac.

[6][8] After the iris has flowered, between June and August,[12][19] it produces an ellipsoid or obovoid (oblong-ovoid),[12][7] light green,[14] seed capsule.

[7][31] Inside, are multiple,[23][31] black-brown seeds,[12][23] which are pyriform (pear shaped) and have a small cream (coloured) aril (appendage).

[12][7] In 1994, a study was carried out to isolate various chemical compounds from the seeds of Iris tectorum, it found an ester 'iristectorene B'.

[40] In 1999, a study was carried out Iris tectorum rhizomes, it found a triterpenoid chemical compound.

[42] In May 2007, a study was carried out on the rhizomes of Iris tectorum, to find various chemical compounds.

[47] In 2013, a molecular phylogenetic (genetic evolution) study was carried out on 16 species of Iris found in Korea.

[21][59] Iris tectorum is native to China, but was first discovered in the 1860s, growing in Japan on the roofs, hence the common name.

Serres Vol.22 page 23 in 1874, with a colour illustration,[6] then published by Hooker in Curtis's Botanical Magazine table 6118 in September, 1874,[5][6] and in the 'Journal of the Royal Horticultural Society' Vol88 page116 in 1963.

[8] It was introduced to England and European cultivation in 1874,[4][6] by Philipp Franz von Siebold, who sent plants to St Petersburg.

[11][51][52] It is found in (central and south western),[7][2][61] China,[36][52][53] within the Chinese provinces, of Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Xizang, Yunnan and Zhejiang.

[55] It grows on forest margins, on sunny banks, in meadows, in damp places and beside water.

[12][11][15] In New Hampshire, as a wild flower, it is found on the edges of lawns and fields, beside roadsides and in compost heaps.

[28][30][54] It is hardy to European Zone H2,[8] meaning it can tolerate temperatures as low as −10,[11] but needs protection from hard frosts.

[25] Iris tectorum has many cultivars including; Like many other irises, most parts of the plant are poisonous (rhizome and leaves), if mistakenly ingested, it can cause stomach pains and vomiting.

[11][9] Despite its toxicity, it is used in Chinese herbal medicine to treat hepatitis and wind damp pains.

[65] The Kam eat fish that have been given fresh Iris tectorum, as medicine to treat stomach aches.

[10][22][27] But also women wanted the iris roots for making hair dye, face powder and corn plasters.

[38] The rhizomes were ground down,[22][54] to make a white powder used for whitening the skin,[10][11][34] similar in look to Geisha girls.

[38] Another theory, was that it was grown in the wet clay and was used to bind the straw thatch together, to stop a roof coming apart.

[23] A final reason known, was that it was planted to avert the 'evil spirits' and a superstition that they prevent disease from affecting the householders.