Rhizome wiry. Leaves flat, 3-4 mm wide, erect, 50-100 cm long, absent in winter. Stem 70-120 cm tall. Spathes brown papery. Flowers 2-5, blue-violet, 6-8 cm wide; late spring. Perianth tube about 1 cm; falls obovate, dark-veined with white signal; standards smaller, obovate, erect.

Europe and N Asia.

The Sino-Siberian Irises are eight species originating from the Himalayas and SW China and require cool climate conditions. Included in this group are:

I. chrysographes Dykes, Gold-veined Iris, from SW China, E Tibet, N Burma has stems 30-70 cm long, unbranched. Leaves 30-70 cm long, 8-15 mm wide, linear, lax, grey-green. Spathes 7-9 cm, green, with long points. Flowers 2, dark purple, about 8 cm wide, fragrant; late spring. Perianth tube 1.5 cm long; falls oblanceolate, bent downwards, usually netted with golden lines; standards narrower, 6 cm long, spreading obliquely. Style branches dark purple, keeled, with short crests. 'Nigra' has pure black flowers.

I. forrestii Dykes,Yunnan Iris from SW China, N Burma and Tibet has rhizome short, thick. Leaves linear, flat, glossy on one side only. Stems 30-40 cm long, unbranched. Spathes 6-7 cm long, green, long-acuminate. Flowers 1-2, light yellow, 6-7 cm wide, fragrant; early summer. Perianth tube 13 mm long; falls obovate, 6.5 cm long, with stripes or spots of purple-brown; standards erect, oblanceolate, 4 cm. Style branches pale yellow, 4 cm.

The Sino-Siberian cultivars are derived from I. forrestii, I. delavayi Micheli and others from the same region.They have flowers in various colours from 7 to 12 cm wide. Siberian hybrids are derived mainly from I. siberica and I. sanguinea Hornem., are mostly blue, violet and white with large falls and smaller standards; ruffled lobes. Plants 15 to 120 cm tall; flowers 7 to 13 cm wide. Colchicine treatment has produced tetraploid flowers in recent years and the latest hybridizing has resulted in wider petals, new forms and an improved but limited colour range, ruffling and some with numerous petaloid stamens resulting in a carnation-like flower. Good garden plants forming neat clumps.

Australian cultivars

Source: Cooke, D. (2005). Iridaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.