• 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

Thunbergia grandiflora

Bengal clock vine

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
Bengal clock vine

© � RHS 2002

  • Other common names Bengal clock vine
    Blue skyflower

    Blue trumpet vine
    Clock vine
    Skyflower
    Sky vine

    see more
  • Genus Thunbergia can be annuals or perennials, often twining climbers, with simple opposite leaves and trumpet-shaped or salver-shaped flowers borne singly in leaf axils, or in racemes, in summer

  • Family Acanthaceae / Acanthaceae

  • Species T. grandiflora is a very vigorous twining evergreen shrub to 6m or more, with heart-shaped, coarsely-toothed leaves and racemes of trumpet-shaped, light violet-blue flowers 7cm across, yellow in the throat

  • Plant range N India

Characteristics

  • Foliage Evergreen

  • Habit Climbing

  • 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

    H1a

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or East-facing

  • Exposure Sheltered

Soil

  • Chalk

    Loam

  • MoistureMoist but well-drained

  • SoilLoam

  • pHAcid, Alkaline, Neutral

Size

  • Ultimate height

    4-8 metres

  • Ultimate spread

    1.5-2.5 metres

  • Time to ultimate height

    5-10 years

How to grow

Cultivation Grow under glass in a loam-based potting compost in bright filtered light with shade from hot sun. When in growth water moderately and apply a balanced liquid fertilizer monthly. Water sparingly at other times

Propagation Propagate by seed or softwood cuttings

Suggested planting locations and garden types Patio & Container Plants

How to care

Pruning Pruning group 11

Pests May be attacked by glasshouse whitefly, glasshouse red spider mite, aphids and scale insects when grown under glass

Diseases Generally disease free

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