Canada thistle
Cirsium arvense (L.) Scop.


Overview


Appearance
Cirsium arvense, a rhizomatous perennial grows from 1-5 ft. (0.3-1.5 m) tall. Roots can grow deep into the ground. Stems do not have conspicuous spines.
Foliage
Leaves are dark green and lanceolate to oblong-lanceolate. They are glabrous above, but their undersides have short, white hairs. They may be pinnatifid and very prickly. Basal leaves are 5-8 in. (12-20 cm) long. Leaves are usually sessile to slightly clasping. Leaf characteristics are variable across different varieties and subspecies.
Flowers
It has male and female plants. Female flowers are flask-shaped, 0.4-0.6 in. (1-1.5 cm) in diameter, and 0.4-0.75 in. (1-2 cm) tall. Female flowers are fragrant, the male flowers are not. Male flowers are smaller and more globose than the female flowers. Flowers range from purple to pink or white. It blooms from June to August.
Fruit
Fruits are tiny, 0.1 in. (2-3 mm) long, about 0.04 in. (1 mm) in diameter, with a white to light brown pappus.
Ecological Threat
Cirsium arvense is most commonly found in agricultural and disturbed sites, or sites that are undergoing restoration. It is shade intolerant and therefore is rarely found within wooded sites, except in clearings. It is found in some dry, sandy sites, but more commonly on the edges of wet habitats such as stream banks and lake shores. In the western and northern U.S. it presents a significant problem in prairie and riparian habitats.

Resources


Selected Images



Maps



EDDMapS Distribution

EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

State Regulated List

State Regulated List - This map identifies those states that list this species on their regulated list. For more information, visit Invasive.org

State Regulated List
Legend
   No Data for this state
   Troublesome or Common weed in one or more crops

Most Troublesome / Most Common Agricultural Weed List
This map identifies those states that consider this species either most troublesome or most common in at least one commodity. For more information, visit the MTMC project page.

Invasive Listing Sources


Taxonomic Rank


Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteridae
Order: Asterales
Family: Asteraceae
Genus: Cirsium
Subject: Cirsium arvense (L.) Scop.

Synonyms and Other Names


Other Common Names:
Californian thistle, creeping thistle, field thistle

Related Scientific Names:
Breea arvensis (L.) Scop. (Synonym)
Breea incana (L.) Scop. (Synonym)
Carduus arvensis (L.) Scop. (Synonym)
Cirsium incanum (L.) Scop. (Synonym)
Cirsium setosum (L.) Scop. (Synonym)
Serratula arvensis (L.) Scop. (Synonym)

Categories


Plants - Forbs/Herbs