About
Onopordum acanthium, cotton thistle or Scotch thistle, is a strong, upright biennial to 3 m tall with oblong, spiny, cobwebby, grey leaves to 30 cm long and rounded, thistle-like, purple flowerheads 5 cm across in summer. A bold and architectural plant for a sunny, well-drained border or wildflower garden.
About the genus
Onopordum are upright biennials with a basal rosette of simple or pinnately lobed, grey-hairy leaves and large, thistle-like, pink or purple flowerheads in summer. Architectural plants for sunny, well-drained borders.
Growing conditions
SunlightFull sun
Soil typeChalk, Loam, Sand
Soil pHAlkaline, Neutral
Soil moistureWell-drained
AspectWest-facing, South-facing
ExposureExposed, Sheltered
UK hardinessH5
Plant details
Plant typeAnnual Biennial
HabitClump forming
FoliageDeciduous
Height2.5-4 metres
Spread0.5-1 metres
Time to full height2-5 years
Suggested usesCottage and informal garden, Wildflower meadow, Wildlife gardens
Native toEurope to C Asia
Care notes
CultivationGrow 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
PruningNo pruning required
PropagationPropagate by seed in containers in a cold frame or in situ in autumn or spring
Pest resistanceMay be susceptible to slugs and snails
Disease resistanceGenerally disease-free