• 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

Silybum marianum

milk thistle

  • Other common names milk thistle
    blessed Mary's thistle

    blessed thistle
    holy thistle
    lady's milk
    lady's thistle
    leaves of Mary
    Mary's thistle
    Our Lady's milk thistle
    Our Lady's thistle
    St Mary's thistle

    see more
  • Synonyms Carduus marianus

  • Family Asteraceae

  • Genus Silybum are large annuals and biennials, with basal rosettes of large, lobed leaves and thistle-like purple flower-heads with spiny bracts in summer

  • Details S. marianum is a robust biennial forming a rosette of large, spiny dark green leaves with prominent white veins, and with purple flower-heads with spiny bracts, in the second year

  • Plant range Mediterranean, SW Europe to Afghanistan


  • Foliage Deciduous

  • 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)




  • Full Sun

  • Aspect South-facing or West-facing

  • Exposure Exposed or Sheltered


  • Loam


  • Sand


  • MoistureWell-drained

  • SoilLoam, Sand

  • pHAlkaline, Neutral


  • Ultimate height 1-1.5 metres

  • Ultimate spread 0.5-1 metres

  • Time to ultimate height 1-2 years

How to grow

Cultivation Grow in poor to medium fertile, well-drained, neutral to slightly alkaline soil in full sun. Protect from excess winter wet

Propagation Propagate by seed sown in late spring or early summer

Suggested planting locations and garden types Flower borders and beds City & Courtyard Gardens Mediterranean Climate Plants Architectural Cottage & Informal Garden

How to care

Pruning No regular pruning required, but flower stems may be removed to keep foliage effect

Pests Generally pest free

Diseases Generally disease free

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