Italian plumeless thistle
(Carduus pycnocephalus)
This species is Introduced in the United States
Native Range
Mediterranean region, southern Europe, northern Africa, and western Asia
Appearance
Italian thistle is an upright forb that typically grows as a winter annual but occasionally grows as a biennial. Plants grow to 4 ft (1.2 m) tall on average from stout taproots. Leaves are alternate, lance-shaped, covered with short, matted hairs on the undersides, and have spines on lobe tips. Stems are slender, narrowly winged, and spiny. Flower heads appear in tight clusters at branch tips. Flower head bracts are long and triangular with cobwebby hairs at their base. Florets are pinkish-purple. There are two types of seeds: cream-colored with tufts of fine hair and brown-colored without.
Impact
Introduced thistles currently infest millions of acres across North America, primarily occurring in or along roadways, waterways, agricultural fields, rangelands, pastures, forests, and disturbed areas. They are responsible for millions of dollars of damage annually in reduced agricultural yields and lowered forage value in grazing systems. Introduced invasive thistles can also displace native vegetation, negatively impacting wildlife and threatening the delicate ecological balance within many habitats.
Reference
Randall, C.B., J.E. Andreas, and J. Milan. 2024. Introduced Thistles: History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2024-8- INTRODUCED THISTLES-P. https://bugwoodcloud.org/resource/files/29168.pdf
Selected Images
Maps
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 Lists - This map identifies those states that have this species on their invasive species list or law.
Invasive Listing Sources
- California Invasive Plant Council
- California Noxious Weeds
- Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
- New Invaders of the Northwest
- Oregon Noxious Weeds
- Pacific Northwest Exotic Pest Plant Council, 1998
- Washington Noxious Weeds
- WeedUS - Database of Plants Invading Natural Areas in the United States
Taxonomic Rank
| Domain: Eukarya |
| Kingdom: Plantae |
| Phylum: Magnoliophyta |
| Class: Magnoliopsida |
| Superorder: Asteranae |
| Order: Asterales |
| Family: Asteraceae |
| Subfamily: Carduoideae |
| Tribe: Cardueae |
| Genus: Carduus |
| Carduus pycnocephalus |
References
Common Name Reference: USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.
Scientific Name Reference: USDA, NRCS. 2010. The PLANTS Database. National Plant Data Center, Baton Rouge, LA, USA.