• AGM plants

    AGM plants have been through a rigourous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Iris versicolor

Blue flag

Blue flag

© � RHS 2002

  • Other common names Blue flag
    Boston iris

    Liver lily
    North American blue flag
    Particoloured iris
    Purple iris
    Snake lily
    Wild iris

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  • Genus Iris may be rhizomatous or bulbous perennials, with narrowly leaves and erect stems bearing flowers with 3 large spreading or pendent fall petals, alternating with 3 erect, often smaller, standard petals, in late winter, spring or early summer

  • Family Iridaceae / Iridaceae

  • Species I. versicolor is a rhizomatous perennial to 80cm in height, with narrow, erect foliage and branched stems bearing several bluish-purple flowers 6-8cm in width, the falls with a conspicuously veined white basal patch

  • Plant range N America


  • Foliage Deciduous

  • Habit Clump-forming

  • Toxicity Ingestion may cause severe discomfort



  • Full Sun

  • Aspect South-facing or West-facing

  • Exposure Sheltered or Exposed


  • Chalk


  • Chalk


  • Chalk


  • MoisturePoorly-drained

  • SoilSand, Clay, Loam

  • pHAcid, Neutral


  • Ultimate height

    0.5-1 metres

  • Ultimate spread

    0.1-0.5 metres

  • Time to ultimate height

    2-5 years

How to grow

Cultivation Grow in moist to wet deep, humus-rich, acid soil in full sun

Propagation Propagate by division from mid-summer to early autumn

Suggested planting locations and garden types Flower borders and beds Low Maintenance Cottage & Informal Garden Wildflower meadow

How to care

Pruning No pruning required

Pests Can be defoliated by sawflies

Diseases Generally disease free

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