• 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 yuccifolium

button snakeroot

button snakeroot

© RHS

  • Other common names button snakeroot
    rattlesnake-master

    rattlesnake's master
    button eryngo

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  • 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 E. yuccifolium is an evergreen perennial with sword-shaped, spiny-edged, blue-grey leaves and branched stems bearing small, egg-shaped white flower-heads in late summer

  • Plant range C & E North America

Characteristics

  • Foliage Evergreen

  • 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)

    H4

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or East-facing

  • Exposure Exposed or Sheltered

Soil

  • Sand

    Sand

  • Loam

    Loam

  • MoistureWell-drained

  • SoilSand, 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 Grow in dry, well-drained, poor to moderately fertile soil in full sun. Protect from winter wet

Propagation Propagate by seed or division

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

How to care

Pruning Cut back after flowering

Pests Slugs and snails may be troublesome

Diseases May be subject to powdery mildews

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