Cultivars
'Alba'
This rhizomatous perennial produces white flowers.

'Exception'
This rhizomatous perennial produces deep purple flowers with large falls.

'Jodlesong'
This has upright long linear, dark green leaves and forms a dense clump up to 1.2 m (4 ft) tall.  It produces deep purple flowers that are marked in bright yellow at the base of the petals.

'Mystic'
This rhizomatous perennial produces purple-blue flowers that have red margins.

'Peter Blue'
This rhizomatous perennial produces mid blue flowers.

'Moonlight Waves'
This rhizomatous perennial produces white flowers with lime green centres.

'Tsuyu-No-Gyokusho'
This rhizomatous perennial has long linear mid green leaves and produces bright yellow flowers with reddish brown markings in the veins at the base of the petals.  The flowers appear in clusters that are held above the foliage appearing during late spring. It is planted around ponds or water features or used in perennial borders.