Onopordum acanthium
cotton thistle
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 thistledown 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
Size
Ultimate height
2.5–4 metresTime to ultimate height
2–5 yearsUltimate spread
0.5–1 metresGrowing conditions
Moisture
Well–drainedpH
Alkaline, NeutralColour & scent
Stem | Flower | Foliage | Fruit | |
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
H5Botanical details
- Family
- Asteraceae
- Native to the UK
- Yes
- Foliage
- Deciduous
- Habit
- Clump forming
- 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
- Wildlife gardens
- Flower borders and beds
Pruning
No pruning required
Pests
Diseases
Generally disease-free
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.