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Grey-green biennial or annual up to 3 metres tall
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Also known as 'cotton thistle' for soft hairs that cover the leaves and stalk
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Introduced from southern Europe and Asia
Scotch thistle
(Onopordum acanthium)
Quick Identification
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Large, grey-green, spiny leaves, covered soft hairs and white veins
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Triangular branching stalk
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Flowers generally large and a light fuchsia 2 to 7 cm.
Impact
Forms dense stands that reduce forage, inhibit movement of livestock and wildlife, and block access to water and forage.
Management
Cutting and bagging the flowers and seed heads and digging out the taproot is effective. Wear thick gloves for the spines. Effective herbicides are available.
Flower
Light fuchsia flowers are 2 to 7 cm across with needle like bracts. They bloom from mid June to mid September.
Leaves & Stems
The plant is a rosette in the first year. The thistle can grow to as much as 3 m tall in the second year and as wide as 2 m. The leaves are large, spiny along the edges, covered by woolly hairs on the top and bottom, with pale veins. The stalk is triangular and branching, sometimes forming a bush-like structure.
Roots
The taproot is long and fleshy.
Reproduction & Dispersal
Plants can regrow from severed roots. Plant spreads primarily by seeds carried by the wind or water, on clothing and fur, or in hay.
Seeds
A single plant can produce 8,400 to 40,000 seeds. They are topped by a pappus allowing seeds to be carried many kilomtres on the wind. They are then remain viable in the soil as much as 30 years.
Preferred Habitat
The thistle grows in pasture, range and crops land, but prefers disturbed areas such as ditches and banks. It favours moist, but well-drained soils and is tolerant of drought.
Interesting Facts
The woolly hairs have been used to stuff pillows.
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