• 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

Crocosmia masoniorum 'Rowallane Yellow'

Giant montbretia 'Rowallane Yellow'

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
Giant montbretia 'Rowallane Yellow'

© � RHS

  • Other common names Giant montbretia 'Rowallane Yellow'

  • Genus Crocosmia are deciduous cormous perennials with erect, sword-shaped leaves and branched spikes of showy, funnel-shaped flowers in summer

  • Family Iridaceae / Iridaceae

  • Species 'Rowallane Yellow' is an erect herbaceous perennial to 80cm, with narrowly sword-shaped leaves and sprays of bright chrome yellow flowers in summer

Characteristics

  • Foliage Deciduous

  • Habit Bushy

  • Hardiness

    Hardiness ratings

    All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

    • H1a - Under glass all year (>15C)
    • H1b - Can be grown outside in the summer (10 - 15)
    • H1c - Can be grown outside in the summer (5 - 10)
    • H2 - Tolerant of low temperatures, but not surviving being frozen (1 to 5)
    • H3 - Hardy in coastal and relatively mild parts of the UK (-5 to 1)
    • H4 - Hardy through most of the UK (-10 to -5)
    • H5 - Hardy in most places throughout the UK even in severe winters (-15 to -10)
    • H6 - Hardy in all of UK and northern Europe (-20 to -15)
    • H7 - Hardy in the severest European continental climates (< -20)
    Old hardiness ratings

    While we update our systems with the new hardiness ratings you may still see old hardiness ratings in your search results. These are denoted as 'Old'.

    • H1 - Requires heated glass
    • H2 - Requires unheated glass
    • H3 - Hardy outside in some regions of the UK
    • H4 - Hardy throughout the UK
    • H1 + H3 - Requires heated glass but may be grown outside in summer

    For full details of the hardiness ratings see

    see more

    H4

Colour

Sunlight

  • Partial Shade

  • Aspect South-facing or West-facing or East-facing

  • Exposure Sheltered

Soil

  • Chalk

    Sand

  • Chalk

    Clay

  • Chalk

    Chalk

  • Chalk

    Loam

  • MoistureMoist but well-drained

  • SoilSand, Clay, Chalk, Loam

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height

    0.5-1 metres

  • Ultimate spread

    0.1-0.5 metres

  • Time to ultimate height

    2-5 years

How to grow

Cultivation Plant 8 to 10cm deep in moderately fertile, humus-rich soil. Lift and divide congested clumps to maintain vigour

Propagation Propagate by division in early spring as growth begins

Suggested planting locations and garden types Banks and Slopes Flower borders and beds City & Courtyard Gardens Coastal Cottage & Informal Garden

How to care

Pruning No pruning required

Pests Generally pest free

Diseases Generally disease free

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