Silybum marianum

RHS Plant Profile
milk thistle

Save a plant

Where do you want to save Silybum marianum?

Plants I own
Wishlist
Go to My Plants
milk thistle Niki Simpson 1998

Other common names

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

Synonyms

Carduus marianus

Annual Biennial
Buy this from Plant Nurseries
8 Suppliers

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

Position

Full sun

Soil Types

Loam, Sand

Max Height

1-1.5 metres

Max Spread

0.5-1 metres

Size

Time to Maturity
1–2 years
Max Spread
0.5-1 metres
Max Height
1-1.5 metres

Growing Conditions

Loam Sand
Moisture
Well–drained
pH
Alkaline or Neutral

Position

Full sun
Aspect
South–facing or West–facing
Exposure
Exposed or Sheltered
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 & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Asteraceae
Native to GB/Ireland
Yes
Foliage
Deciduous
Habit
Columnar upright
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
Name Status
Correct
Plant Range
Mediterranean, SW Europe to Afghanistan

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

  • City and courtyard gardens
  • Mediterranean climate plants
  • Architectural
  • Cottage and informal garden
  • Flower borders and beds

Pruning

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

Pests

Generally pest-free

Diseases

Generally disease-free