iris 'Black Swan'

Grow in well-drained, fertile, neutral to slightly acidic soil in full sun. Do not cover the rhizomes with mulch, or allow other plants to shade them; sun on the rhizomes encourages flowering. Give a high potash feed in spring and divide every three to four years. See also bearded iris cultivation

Remove any dying foliage in autumn; old flower stems can be cut down after flowering

Propagate by division of rhizomes from midsummer to early autumn; see dividing irises

May be attacked by slugs, snails and thrips

May be subject to iris rhizome rot, a leaf spot and a virus; see iris diseases