Not the plant you're looking for? Search over 300,000 plants
Annual Biennial

Onopordum acanthium
  • RHS Plants for pollinators

cotton thistle

O. acanthium is a robust, upright biennial to 3m tall, with oblong, spiny, cobwebby grey leaves to 30cm long, and rounded, thistle-like purple flower heads 5cm across in summer

Other common names
Argentine thistle
down thistle
see moregiant thistle
musk thistle
oak thistle
oat thistle
Queen Mary's thistle
Scotch thistle
Scots thistle
silver thistle
star thistle
thistle-upon-thistle
Buy this plant
Size
Ultimate height
2.5–4 metres
Time to ultimate height
2–5 years
Ultimate spread
0.5–1 metres
Growing conditions
Chalk
Loam
Sand
Moisture
Well–drained
pH
Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green Grey Silver Grey Silver
Summer Green Grey Silver Purple Grey Silver
Autumn
Winter
Position
  • Full sun
Aspect

West–facing or South–facing

Exposure
Exposed or Sheltered
Hardiness
H5
Botanical details
Family
Asteraceae
Native to the UK
Yes
Foliage
Deciduous
Habit
Bushy
Genus

Onopordum are are upright biennials with a basal rosette of simple or pinnately lobed, grey-hairy leaves and large, thistle-like, pink or purple flower-heads in summer

Name status

Correct

Plant range
Europe to C Asia

How to grow

Cultivation

Grow in fertile, well-drained neutral to slightly alkaline soil in full sun; may self-seed freely and is ideal for a gravel garden or wild areas

Propagation

Propagate by seed in containers in a cold frame or in situ in autumn or spring

Suggested planting locations and garden types
  • Cottage and informal garden
  • Wildflower meadow
  • Flower borders and beds
Pruning

No pruning required

Pests

Slugs and snails may damage the foliage

Diseases

Generally disease free

My Garden

Your free RHS gardening coach

Keep track of your plants with reminders & care tips – all to help you grow successfully

My plants
My calendar

My plants

My calendar

My ideas
Manage membership

My ideas

My advice

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.