• AGM plants

    AGM plants have been through a rigorous 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

Geranium 'Johnson's Blue'

geranium 'Johnson's Blue'

  • Other common names geranium 'Johnson's Blue'

  • Family Geraniaceae

  • Genus Geranium can be annuals, biennials and perennials, herbaceous or evergreen, with rounded, usually palmately lobed or divided leaves, and lax inflorescences of rounded, 5-petalled flowers

  • Details 'Johnson's Blue' is a clump-forming rhizomatous perennial to 30cm, with deeply lobed leaves and long-stalked flowers 5cm in width, with rounded, dark-veined, lavender-blue petals


  • Foliage Deciduous

  • Habit Clump-forming

  • 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)




  • Full Sun

  • Partial Shade

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

  • Exposure Exposed or Sheltered


  • Chalk


  • Chalk


  • Chalk


  • Chalk


  • MoistureMoist but well-drained, Well-drained

  • SoilSand, Loam, Chalk, Clay

  • pHAcid, Alkaline, Neutral


  • Ultimate height 0.1-0.5 metres

  • Ultimate spread 0.5-1 metres

  • Time to ultimate height 2-5 years

How to grow

Cultivation Grow in any, moderately fertile soil apart from waterlogged soils. Full sun or partial shade is best but shade is tolerated

Propagation Propagate by division in spring or propagate by basal cuttings in early to mid spring and root with bottom heat

Suggested planting locations and garden types Flower borders and beds Ground Cover Underplanting of Roses and Shrubs Low Maintenance Cottage & Informal Garden

How to care

Pruning Remove flowered stems and old leaves to encourage the production of fresh leaves and flowers

Pests Can get vine weevil, capsid bug and sawflies

Diseases May be affected by a downy mildew and powdery mildews

Advertise here

Did you find the information you were looking for?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now