Canada thistle

 Plants: Forbs/Herbs
Magnoliopsida > Asterales > Asteraceae > Cirsium arvense (L.) Scop.
Synonym(s): Californian thistle, creeping thistle, field thistle
Canada thistle is a tall, erect, spiny, perennial, herbaceous plant that grows to 4 ft. (1.2 m) tall. It has an extensive creeping rootstock. The leaves are lance-shaped, irregularly lobed, 2-6 in. (5-15 cm) long with prickly margins. The stems are ridged and hairy. The flowers are purple to white and can be up to 0.5 in. (1.8 cm) in diameter. Flowering occurs in late June to August. The small fruit, called achenes, are 1 to 1.5 in. (2.5-3.8 cm) long and have a feathery pappus which allows them to be dispersed further by wind. Numerous species of thistle occur in North America, and while some are invasive, many are native. Often the species are difficult to distinguish. Canada thistle can invade a variety of open habitats including prairies, savannas, fields, pastures, wet meadows and open forests. It forms dense stands which can shade out and displace native vegetation. Once established it spreads rapidly and is difficult to remove. Canada thistle is native to Europe and Asia and was accidentally introduced to North America in the 1600s.

39 records

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Image Subject Scientific Name Descriptor
1318030 rust mite Aceria anthocoptes (Nal.) Adult(s)
1929048 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Adult(s)
0024022 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Adult(s)
0025041 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Adult(s)
0025023 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Larva(e)
0024023 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Larva(e)
0024024 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Larva(e)
1929049 Canada thistle stem mining weevil Ceutorhynchus litura (Fabricius) Larva(e)
1929050 Canada thistle bud weevil Larinus planus (Fabricius) Adult(s)
1929051 Canada thistle bud weevil Larinus planus (Fabricius) Adult(s)
0026033 Canada thistle bud weevil Larinus planus (Fabricius) Adult(s)
0026034 Canada thistle bud weevil Larinus planus (Fabricius) Adult(s)
0026035 Canada thistle bud weevil Larinus planus (Fabricius) Damage
0026032 Canada thistle bud weevil Larinus planus (Fabricius) Damage
0026036 Canada thistle bud weevil Larinus planus (Fabricius) Larva(e)
1929052 Canada thistle bud weevil Larinus planus (Fabricius) Larva(e)
5359599 puccinia rusts Puccinia spp. Pers. Sign
0025100 musk thistle head weevil Rhinocyllus conicus (Frölich)
0024025 Canada thistle stem gall fly Urophora cardui (Linnaeus) Adult(s)
1929053 Canada thistle stem gall fly Urophora cardui (Linnaeus) Adult(s)
1929054 Canada thistle stem gall fly Urophora cardui (Linnaeus) Adult(s)
5304034 Canada thistle stem gall fly Urophora cardui (Linnaeus) Adult(s)
5304035 Canada thistle stem gall fly Urophora cardui (Linnaeus) Adult(s)
5358617 Canada thistle stem gall fly Urophora cardui (Linnaeus) Adult(s)
5358618 Canada thistle stem gall fly Urophora cardui (Linnaeus) Damage
5304036 Canada thistle stem gall fly Urophora cardui (Linnaeus) Damage
5304037 Canada thistle stem gall fly Urophora cardui (Linnaeus) Damage
1929055 Canada thistle stem gall fly Urophora cardui (Linnaeus) Damage
0024026 Canada thistle stem gall fly Urophora cardui (Linnaeus) Damage
0024027 Canada thistle stem gall fly Urophora cardui (Linnaeus) Immature(s)
1246085 painted lady butterfly Vanessa cardui (Linnaeus) Adult(s)
1246089 painted lady butterfly Vanessa cardui (Linnaeus) Adult(s)
1246084 painted lady butterfly Vanessa cardui (Linnaeus) Egg(s)
1246087 painted lady butterfly Vanessa cardui (Linnaeus) Larva(e)
1246088 painted lady butterfly Vanessa cardui (Linnaeus) Larva(e)
1246081 painted lady butterfly Vanessa cardui (Linnaeus) Larva(e)
1246082 painted lady butterfly Vanessa cardui (Linnaeus) Larva(e)
1246083 painted lady butterfly Vanessa cardui (Linnaeus) Larva(e)
1246086 painted lady butterfly Vanessa cardui (Linnaeus) Pupa(e)


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