• 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

Eryngium planum 'Bethlehem'

blue eryngo 'Bethlehem'

blue eryngo 'Bethlehem'

© RHS 1999

  • Other common names blue eryngo 'Bethlehem'

  • Family Apiaceae

  • Genus Eryngium can be annuals, biennials or perennials with simple or divided leaves, often spiny edged, and cone-like flower-heads often surrounded by an involucre of conspicuous spiny bracts

  • Details 'Bethlehem' is a perennial forming a clump of oblong dark green leaves and branched stems bearing small, slate-blue flower-heads with narrow bracts


  • Foliage Evergreen

  • 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

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

  • Exposure Exposed


  • Chalk


  • Chalk


  • Chalk


  • MoistureWell-drained

  • SoilSand, Loam, Chalk

  • pHAcid, Alkaline, 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 dry, well-drained soil that is poor to moderately fertile. Full sun is essential as is protection from winter wet

Propagation Propagate by root cuttings in late winter

Suggested planting locations and garden types Flower borders and beds Cut Flowers Coastal Cottage & Informal Garden Gravel Garden Wildlife Gardens

How to care

Pruning Although you can cut back flower stems after flowering the seedheads are a very attractive feature so are usually left over winter

Pests Can get leaf and bud eelworms

Diseases May be affected by powdery mildews and root rot

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