• 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

Astrophytum myriostigma

bishop's cap

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
bishop's cap

© RHS

  • Other common names bishop's cap
    bishop's mitre

    bishop's hood
    monk's hood

    see more
  • Family Cactaceae

  • Genus Astrophytum are compact perennial cacti with ribbed, spherical or columnar stems bearing woolly, sometimes also shortly spiny areoles, and large, solitary, funnel-shaped flowers in summer, followed by red or green berries

  • Details A. myriostigma is a cactus forming a spherical or shortly columnar, ribbed grey-green spineless plant to 20cm tall; light yellow flowers 5cm across, sometimes reddish in centre, open in summer

  • Plant range NE Mexico

Characteristics

  • Foliage Evergreen

  • Habit Columnar/Upright

  • 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)

    H2

Colour

Sunlight

  • Full Sun

  • Aspect South-facing or West-facing

  • Exposure Sheltered

Soil

  • Chalk

    Sand

  • Chalk

    Chalk

  • MoistureWell-drained

  • SoilSand, Chalk

  • pHAlkaline, Neutral

Size

  • Ultimate height 0.1-0.5 metres

  • Ultimate spread 0-0.1 metre

  • Time to ultimate height 10-20 years

How to grow

Cultivation Under glass grow in cactus compost with added limestone chippings, in bright filtered light. Lightly water in growing season but keep dry when dormant. In warmer climates outdoors grow in sharply drained, poor, slightly alkaline soil in full sun.

Propagation Propagate by seed sown at 21°C (70°F) in early spring

Suggested planting locations and garden types Patio & Container Plants

How to care

Pruning No pruning required

Pests mealybugs may be a problem

Diseases Generally disease free

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