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Canadian Fleabane

Conyza canadensis

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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 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, Cotton Thistle, 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, Trifid Bur-marigold, Tuberous Thistle, Tyneside Leopardplant, Viper's Grass, Wall Lettuce, Welsh Groundsel, Welted Thistle, 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, meadows, roadsides, sand dunes, towns, walls, wasteland.

Yellow, many petals
Many-flowered. Small tubular 4-lobed yellow disc florets, yellow-green bracts that are only slightly downy, very short white rays.
Seedhead, white and bristly pappus. Cylindrical and elongated but widest above the middle.
Slender, simple, unstalked, linear leaves. Upper leaves have toothed margins and lower leaves have smooth margins.
Crushed leaves and stems smell unpleasantly like carrot.
Other Names:
Bitterweed, Blood Stanch, Butterweed, Canadian Horseweed, Colt's Tail, Cow's Tail, Fireweed, Hogweed, Horse Tongue, Horseweed, Mare's Tail, Mule Tail, Prideweed.
Frequency (UK):

Similar Species

Other Information


Conyza canadensis, also known as Canadian horseweed or Canadian fleabane, is a species of wildflower in the daisy family (Asteraceae). It is native to North America, and is found throughout the United States and Canada.

Conyza canadensis is an annual or perennial herb that can grow up to 3 meters tall, with a hairy stem and hairy leaves that are alternate and lance-shaped. The plant produces small, yellow composite flowerheads that bloom from summer to fall. The flowers are typically 1/2-1 inch in diameter and are followed by small achenes (fruits) that are equipped with fluffy bristles to help disperse them by wind.

This plant is quite adaptable and can grow in a variety of soil types and in full sun or partial shade. It can also tolerate drought and poor soil. It can be found in a wide variety of habitats, including roadsides, fields, and disturbed areas, as well as gardens, meadows, and wildflower gardens.

Conyza canadensis is considered invasive in many regions and can outcompete native plants in areas where it has been introduced. It is propagated by seed, which are dispersed by wind, animals, and water. To control it, manual removal, using mulch or mulch combined with herbicide application are some of the methods.

It's worth noting that this plant contains a compound called pyrrolizidine alkaloids (PA) which may cause liver damage if consumed in large amounts, specially if the plant is a biennial or perennial. Therefore, it is not recommended to use it as a medicinal or food plant without proper knowledge and guidance.


Canadian Fleabane, Conyza canadensis, is a herbaceous plant that belongs to the Asteraceae family. It is commonly found throughout North America, but its origins are believed to be in the eastern and central regions of the continent. Canadian Fleabane is also known by other common names such as horseweed, butterweed, and coltstail.

Appearance and Habitat

Canadian Fleabane can grow up to six feet tall and has an upright, branched stem that is covered in fine hairs. Its leaves are narrow, oblong, and alternate along the stem, and can grow up to four inches long. The plant produces small, white or pale pink flowers that are clustered together in large groups at the top of the stem. The flowers are followed by small, light brown seeds that are spread by the wind.

Canadian Fleabane thrives in disturbed areas, such as roadsides, fields, and pastures, but it can also grow in undisturbed habitats. It can tolerate a wide range of soil types and pH levels, and it can grow in both wet and dry conditions. It is an annual or biennial plant, which means it completes its life cycle in one or two years.


Canadian Fleabane has been used for various medicinal purposes by Indigenous peoples and early settlers. It was traditionally used to treat respiratory ailments, such as asthma and coughs, as well as digestive issues, such as diarrhea and dysentery. The plant was also used as a natural insect repellent and as a topical treatment for skin conditions like eczema and psoriasis.

In modern times, Canadian Fleabane is considered a weed that can be difficult to control in agricultural fields. However, some farmers have found that the plant can provide some benefits as a cover crop. The plant's deep roots can help to break up compacted soil and improve soil health, and its biomass can provide organic matter for the soil.

Canadian Fleabane is a common plant in North America that has a long history of use in traditional medicine. While it is considered a weed by some, it can also have some benefits as a cover crop in agricultural settings. As with any medicinal plant, it is important to consult with a healthcare professional before using it for any health-related purposes.

More Information about Canadian Fleabane

Canadian Fleabane is a highly adaptable plant that has been able to thrive in many different environments. In fact, it has become a problematic weed in many agricultural areas due to its ability to grow quickly and compete with crops for nutrients and water. Because of this, farmers and gardeners often try to control Canadian Fleabane populations using herbicides or other methods.

However, there is growing interest in using more sustainable methods to manage Canadian Fleabane and other weeds. For example, some farmers are exploring the use of cover crops, crop rotation, and other management techniques that can help to prevent the growth of weeds without relying on chemical herbicides.

Beyond its potential uses in agriculture, Canadian Fleabane has also been studied for its potential as a source of natural bioactive compounds. Researchers have identified several compounds in the plant that may have medicinal properties, including anti-inflammatory and antioxidant effects. However, more research is needed to fully understand the potential health benefits of Canadian Fleabane and how it can be used in modern medicine.

Canadian Fleabane is a fascinating plant that has a long history of use in traditional medicine and continues to be studied for its potential benefits. As with any plant, it is important to use caution and consult with a healthcare professional before using it for any health-related purposes.

Canadian Fleabane also plays an important role in the ecology of North America. Its small, wind-dispersed seeds can travel long distances and help to establish new populations in different areas. In addition, the plant is a valuable source of food and habitat for a variety of insects, birds, and other wildlife.

Despite its benefits to the environment and potential medicinal uses, Canadian Fleabane is also considered an invasive species in some areas. This is due to its ability to outcompete native plant species and disrupt the balance of local ecosystems. As such, it is important to be aware of the potential impact of introducing Canadian Fleabane into new areas, and to take steps to prevent its spread.

In some cases, Canadian Fleabane can also be harmful to livestock, as it contains alkaloids that can be toxic in large quantities. As such, it is important for farmers and ranchers to monitor their fields and pastures for the presence of Canadian Fleabane and other potentially harmful plants.

Canadian Fleabane is a complex and multifaceted plant that has a rich history and many potential uses. As research continues, we may learn even more about this fascinating plant and its role in North American ecology and traditional medicine.

One interesting fact about Canadian Fleabane is that it has become resistant to certain herbicides, including glyphosate. This resistance has been documented in agricultural areas across North America and has made it even more difficult for farmers to manage populations of the plant. As a result, there is a growing interest in exploring alternative methods for controlling Canadian Fleabane and other resistant weeds, such as the use of integrated pest management strategies and cover crops.

In addition to its potential medicinal properties, Canadian Fleabane has also been studied for its potential as a biofuel crop. Researchers have found that the plant can produce significant amounts of biomass, which can be converted into biofuels such as ethanol and biodiesel. While there are still some challenges to be overcome in terms of harvesting and processing the plant, it is an exciting area of research that could have important implications for the future of renewable energy.

Canadian Fleabane is just one of many fascinating and unique plants that can be found throughout North America. From the towering redwoods of California to the delicate wildflowers of the Great Plains, there is no shortage of natural beauty to be found on this continent. By learning more about the plants and animals that make up our ecosystems, we can better appreciate the diversity and complexity of the natural world and work to protect it for future generations.

One interesting aspect of Canadian Fleabane is its ability to hybridize with other species of Conyza, which has led to the creation of several new hybrid species. For example, the hybrid species Conyza x hybrida has been identified in several regions of North America, including the southeastern United States and southern Ontario. These hybrid species can be more difficult to control than the original species, as they may have different characteristics or resistances to certain herbicides.

Canadian Fleabane also has an interesting cultural history. It has been used for centuries by Indigenous peoples in North America for a variety of purposes, including as a medicinal plant, a source of fiber, and a natural dye. The plant has also been used in traditional Chinese medicine to treat a range of ailments, from respiratory problems to digestive issues.

In modern times, Canadian Fleabane has been the subject of controversy due to its potential impact on agricultural productivity. Farmers and other stakeholders have debated the best ways to manage populations of the plant, with some advocating for increased use of herbicides and others promoting more sustainable and integrated pest management practices.

Despite its status as an invasive weed, Canadian Fleabane is a fascinating and important part of North American ecology and culture. By learning more about this plant and other invasive species, we can work to develop more effective strategies for managing them and protecting the health of our natural ecosystems.


Canadian Fleabane filmed at Ainsdale and Crosby on the 3rd July 2023.


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Distribution Map

Reproduced by kind permission of the BSBI.

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