Scotch Thistle

(Onopordum acanthium)

Photos

Rosette

rosette

Pre-bloom

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Mature plant

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Flower

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Flower / seed head

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Seed Head post bloom

seed head

BACKGROUND

Scotch thistle is native to Europe and eastern Asia. It grows well in waste areas, pastures, rangeland, and along canal and stream banks.

DESCRIPTION

This biennial plant commonly grows 3 to 8 feet tall, but it may grow as high as 12 feet. Rosettes may be 4 feet wide. Large, spiny leaves are covered with dense hair, giving a grayish, blue-green coloration. Stems are winged. The flowers are violet to reddish with spine tipped bracts, blooming in mid-summer.

CONTROL

Biocontrol research is currently being conducted. Herbicides can offer good-to-excellent control when applied between rosette and pre-bud stages.