The strong, sturdy stem supports a single large flower in spring, between April and June.

The large flowers are very variable in colouring, ranging from a pale greenish, grey, white, or creamy-yellow background colour, which is then covered with many purplish-brown, purple, or nearly black, spots, dots, short broken lines, or veining.

[5] The stem has pale green spathes, (leaves of the flower bud), that are between 10–12.5 cm (4–5 in) long.

[4][15][16]: 191 The large flowers are between 13–20 cm (5–8 in) in diameter,[4][11][14] they are the largest of the Oncocyclus series,[10] (including I. susiana,[5][17]) and of all irises,[8][15][18] except the Japanese hybrids.

[4][8][9] Which is then covered with many brown,[11] purplish-brown,[19][21] purple,[2][9][15] violet,[17] or nearly black,[4] spots, dots,[6][9] short broken lines,[8] or veining.

[5] The massed purple dots or lines on a creamy white background creates a soft grey flower, when seen from a distance.

[4] In the centre of the falls, is a dark,[16]: 191  purple signal patch,[13]: 129  which is variable in size, (between large and very small,[8][15][21] ) and can be hidden under the beard.

[6] It has a 12.5–17.5 cm (5–7 in) long pedicel, with a short perianth tube,[6] it has white filaments and anthers that are often tipped purple.

[4][6] As most irises are diploid, having two sets of chromosomes, this can be used to identify hybrids and classification of groupings.

Gates,[24] an American Missionary staying in Mardin, Northern Mesopotamia,[15] (now part of Turkey).

[25] 'Iris gatesii' was found near Mardin,[9] in the mountains of Kurdistan,[8] by the botanist, collector and bulb nurseryman Paul Sintenis,[8] who worked for Mr. Max Leichtlin (from Baden-Baden, Germany),[6][8] with the help of Rev.

[3] It gained an FCC ('First Class Certificate', awarded by the RHS,[27]) in 1891 when shown by Van Tubergen (bulb nursery).

[20] Some sources state that it is found in Armenia,[5][24] but it range is more to the north of that region,[6] in South-eastern Turkey,[19][30][31] (within the districts of Urfa, Mardin and Siirt).

[4] It grows on rocky limestone hillsides,[9][11] on steppes,[8] on slopes and in rock crevices.

[33] Due to its range being much farther north than most Oncocyclus irises,[4] it is more hardy in cultivation,[8] than others.

[7][35] It prefers sites in full sun,[7][20] and can be grown in raised bed,[34] or an open border.

[6] It likes moisture at the root tips, but the rhizomes are liable to rot in excessive water.

[39] In 1897, an illustration in The Garden magazine of 31 July, showed a border in Mr Van Tubergen's nursery with 400 flowers, which are the results of 3 seasons of cultivation of the irises.

[17][52] Like many other irises, most parts of the plant are poisonous (rhizome and leaves), and if mistakenly ingested can cause stomach pains and vomiting.