Wall Iris (Iris tectorum) is a native of China, growing on forest edges, meadows, sunny banks, at 500 to 3,500 m (1,600 to 11,500 ft) elevation. Its native habitat is uncertain because it is widely cultivated in China, Bhutan (where it has naturalized), and India. It spreads with creeping rhizomes and has bluish-violet flowers. A white flowered variety has been named Iris tectorum f. alba (Dykes).

Source: http://en.wikipedia.org/wiki/Iris_tectorum