Open the Advanced Search

Cotton Thistle

Onopordum acanthium

Please keep in mind that it is illegal to uproot a plant without the landowner's consent and care should be taken at all times not to damage wild plants. Wild plants should never be picked for pleasure and some plants are protected by law.
For more information please download the BSBI Code of Conduct PDF document.


Plant Profile

Flowering Months:
Asteraceae (Daisy)
Also in this family:
Alpine Blue Sow-thistle, Alpine Cotula, Alpine Fleabane, Alpine Saw-wort, Annual Ragweed, Annual Sunflower, Argentine Fleabane, Autumn Hawkbit, Autumn Oxeye, Beaked Hawksbeard, Beggarticks, Bilbao Fleabane, Black Knapweed, Black-eyed Susan, Blanketflower, Blue Fleabane, Blue Globe-thistle, Bristly Oxtongue, Broad-leaved Cudweed, Broad-leaved Ragwort, Brown Knapweed, Butterbur, Buttonweed, Cabbage Thistle, Canadian Fleabane, Canadian Goldenrod, Carline Thistle, Chalk Knapweed, Chamois Ragwort, Changing Michaelmas Daisy, Chicory, Chinese Mugwort, Chinese Ragwort, Coltsfoot, Common Blue Sow-thistle, Common Cat's-ear, Common Cudweed, Common Daisy, Common Dandelion, Common Fleabane, Common Goldenrod, Common Groundsel, Common Michaelmas Daisy, Common Mugwort, Common Ragwort, Common Wormwood, Coneflower, Confused Michaelmas Daisy, Corn Chamomile, Corn Marigold, Cornflower, Cottonweed, Creeping Thistle, Daisy Bush, Dwarf Cudweed, Dwarf Thistle, Early Goldenrod, Eastern Groundsel, Eastern Leopardsbane, Elecampane, English Hawkweed, Fen Ragwort, Feverfew, Field Fleawort, Field Wormwood, Fox and Cubs, French Tarragon, Gallant Soldier, Garden Lettuce, Giant Butterbur, Glabrous-headed Hawkweed, Glandular Globe-thistle, Glaucous Michaelmas Daisy, Globe Artichoke, Globe-thistle, Goat's Beard, Golden Ragwort, Golden Samphire, Goldilocks Aster, Grass-leaved Goldenrod, Great Lettuce, Greater Burdock, Greater Knapweed, Grey-headed Hawkweed, Guernsey Fleabane, Hairless Blue Sow-thistle, Hairless Leptinella, Hairy Michaelmas Daisy, Harpur Crewe's Leopardsbane, Hawkweed Oxtongue, Heath Cudweed, Heath Groundsel, Hemp Agrimony, Highland Cudweed, Hoary Mugwort, Hoary Ragwort, Hybrid Knapweed, Intermediate Burdock, Irish Fleabane, Jersey Cudweed, Jerusalem Artichoke, Lance-leaved Hawkweed, Lavender-cotton, Leafless Hawksbeard, Least Lettuce, Leopardplant, Leopardsbane, Leptinella, Lesser Burdock, Lesser Hawkbit, Lesser Sunflower, London Bur-marigold, Magellan Ragwort, Marsh Cudweed, Marsh Hawksbeard, Marsh Ragwort, Marsh Sow-thistle, Marsh Thistle, Meadow Thistle, Melancholy Thistle, Mexican Fleabane, Milk Thistle, Mountain Everlasting, Mouse-ear Hawkweed, Musk Thistle, Narrow-leaved Cudweed, Narrow-leaved Hawkweed, Narrow-leaved Michaelmas Daisy, Narrow-leaved Ragwort, New England Hawkweed, New Zealand Holly, Nipplewort, Nodding Bur-marigold, Northern Hawksbeard, Norwegian Mugwort, Oxeye Daisy, Oxford Ragwort, Pearly Everlasting, Perennial Cornflower, Perennial Ragweed, Perennial Sow-thistle, Perennial Sunflower, Pineapple Mayweed, Plantain-leaved Leopardsbane, Ploughman's Spikenard, Plymouth Thistle, Pontic Blue Sow-thistle, Pot Marigold, Prickly Lettuce, Prickly Sow-thistle, Purple Coltsfoot, Rayed Tansy, Red Star Thistle, Red-seeded Dandelion, Red-tipped Cudweed, Robin's Plantain, Roman Chamomile, Rough Cocklebur, Rough Hawkbit, Rough Hawksbeard, Russian Lettuce, Safflower, Salsify, Saw-wort, Scented Mayweed, Scentless Mayweed, Sea Aster, Sea Mayweed, Sea Wormwood, Seaside Daisy, Shaggy Mouse-ear Hawkweed, Shaggy Soldier, Shasta Daisy, Shetland Mouse-ear Hawkweed, Shrub Ragwort, Sicilian Chamomile, Silver Ragwort, Slender Mugwort, Slender Thistle, Small Cudweed, Small Fleabane, Smooth Cat's-ear, Smooth Hawksbeard, Smooth Sow-thistle, Sneezeweed, Sneezewort, Spear Thistle, Spotted Cat's-ear, Spotted Hawkweed, Sticky Groundsel, Stinking Chamomile, Stinking Hawksbeard, Tall Fleabane, Tall Mouse-ear Hawkweed, Tansy, Thin-leaved Sunflower, Treasureflower, Trifid Bur-marigold, Tuberous Thistle, Tyneside Leopardplant, Viper's Grass, Wall Lettuce, Welsh Groundsel, Welted Thistle, White African Daisy, White Butterbur, White Buttons, Willdenow's Leopardsbane, Winter Heliotrope, Wood Burdock, Wood Ragwort, Woody Fleabane, Woolly Thistle, Yarrow, Yellow Chamomile, Yellow Fox and Cubs, Yellow Oxeye, Yellow Star Thistle, Yellow Thistle, York Groundsel
Life Cycle:
Maximum Size:
3 metres tall
Fields, gardens, grassland, hedgerows, meadows, roadsides, wasteland.

Purple, many petals
Solitary, pale purple, globe-shaped flowers, up to 6cm across. Very spiny bracts. Pollinated by bees.
Grey, 5mm long. The fruit has a brown pappus attached to the end of it. The pappus is twice the length of the seed. In fruit from August to October.
Very spiny, oblong, alternate leaves. The stems are winged and have triangular spines. Covered in many fine hairs making the plant look silvery-grey. This biennial is our tallest Thistle in the UK.
Other Names:
Argentine Thistle, Down Thistle, Giant Thistle, Musk Thistle, Oak Thistle, Oat Thistle, Queen Mary's Thistle, Scotch Cottonthistle, Scotch Thistle, Scots Thistle, Silver Thistle, Star Thistle, Thistle-upon-thistle.
Frequency (UK):
Occasionally seen  

Other Information


Onopordum acanthium, also known as Scotch thistle or cotton thistle, is a biennial or short-lived perennial herb native to Europe, Asia and North Africa. It is typically found in grassland, meadows, and disturbed areas such as roadsides and pastures. The plant has a tall, spiky stem and produces large, pink or purple flower heads. It is considered a weed and invasive in many countries, it is known to outcompete native vegetation and reduce forage for livestock. Control methods include mechanical removal, grazing, and the use of herbicides. Onopordum acanthium has been traditionally used for medicinal purposes, such as for treating liver and gallbladder complaints, and the stem and leaves can be eaten and used as a vegetable or in salads.


Cotton Thistle, Onopordum acanthium, is a plant species that belongs to the family Asteraceae. This plant is also commonly referred to as Scotch thistle, and it is native to Europe, North Africa, and Asia. It is considered to be an invasive species in many parts of the world, including North America. In this blog, we will be discussing the features and characteristics of this plant and why it is considered invasive.

Features and Characteristics of Cotton Thistle

Cotton Thistle is a biennial plant that can grow up to 3 meters in height. It has a large, spiny rosette of leaves that can be up to 50 cm in diameter. The leaves are green and covered with white, woolly hairs. The plant also has large, showy, purple or pink flower heads that are surrounded by spiny bracts. The flower heads are up to 10 cm in diameter and bloom from June to September.

The seeds of the Cotton Thistle are dispersed by wind and animals, and they can remain viable in the soil for up to 10 years. The plant is also capable of vegetative reproduction, as it can sprout from the roots of the plant. This makes it very difficult to control once it becomes established.

Why Cotton Thistle is Considered Invasive

Cotton Thistle is considered to be an invasive species in many parts of the world, including North America. This is due to its ability to outcompete native vegetation and dominate the landscape. The plant's large size, spiny leaves, and profuse seed production make it difficult for native species to compete for resources such as light, water, and nutrients.

The presence of Cotton Thistle can also have negative impacts on wildlife. The spiny leaves and stems of the plant can make it difficult for animals to move through an area and access food and shelter. The plant also has a negative impact on grazing lands, as it is unpalatable to most livestock.

Control and Management of Cotton Thistle

Controlling and managing the spread of Cotton Thistle can be a challenging task. The plant is highly adaptable and can tolerate a wide range of conditions, including poor soil and drought. Effective control measures include removing the plant by hand, using herbicides, or a combination of both.

When removing the plant by hand, it is important to remove as much of the root system as possible to prevent regrowth. Herbicides can be used to control the growth of the plant, but it is important to choose the right product for the specific situation. Some herbicides are more effective on young plants, while others are better suited for mature plants.

Cotton Thistle is a plant species that is native to Europe, North Africa, and Asia. It is considered to be an invasive species in many parts of the world, including North America, due to its ability to outcompete native vegetation and dominate the landscape. Control and management of this plant can be a challenging task, but it is important to take steps to prevent its spread and protect native ecosystems.

More Information

In addition to the impacts on native ecosystems, Cotton Thistle can also have negative impacts on agricultural crops. The plant's large size and spiny leaves make it difficult to harvest crops, and the plant can also reduce crop yields by competing for resources.

In some areas, Cotton Thistle is being used for ornamental purposes, despite its invasive nature. This is due to its attractive purple or pink flowers and large size. However, it is important to be mindful of the potential impacts of the plant and to only use it in appropriate and controlled settings.

One way to control the spread of Cotton Thistle is through biological control methods. This involves the use of natural predators or parasites to control the population of the plant. For example, the thistle stem weevil (Rhynchites auctus) is a natural predator of Cotton Thistle and can be used to control its growth.

In addition to biological control methods, physical barriers can also be used to prevent the spread of Cotton Thistle. For example, mulching around native vegetation can help to prevent the seeds of the plant from germinating. Regular monitoring and early detection of new infestations is also important in order to prevent the plant from becoming established in new areas.

Overall, it is important to be aware of the impacts of Cotton Thistle and to take steps to prevent its spread. This can help to protect native ecosystems, agricultural crops, and wildlife, and to ensure that the environment remains healthy and resilient.

Another important aspect to consider when it comes to Cotton Thistle is its cultural and historical significance. The plant has been used for various purposes throughout history, such as for medicinal purposes, as a source of food, and as a source of fibers for weaving.

In some cultures, the plant has also been associated with spiritual and religious beliefs. For example, in ancient Celtic cultures, the plant was considered to be sacred and was associated with the goddess Brigid. In Scotland, the plant is considered to be a symbol of national pride and is often referred to as the "Scotch Thistle".

Despite its cultural and historical significance, it is important to recognize that Cotton Thistle can have significant negative impacts on the environment. In many areas, the plant is considered to be a noxious weed and measures are taken to control its spread.

In conclusion, Cotton Thistle is a plant species with a rich history and cultural significance. However, it is also an invasive species that can have significant negative impacts on the environment. It is important to recognize both the positive and negative aspects of the plant, and to take appropriate measures to control its spread and protect the environment. This can include using biological control methods, physical barriers, and regular monitoring and early detection of new infestations.


Cotton Thistles at Orford Castle, Suffolk on the 26th June 2022.


Please remember to Like and Subscribe to the WildFlowerWeb YouTube channel at

Distribution Map

Reproduced by kind permission of the BSBI.

Click to open an Interactive Map