slenderflower thistle
Carduus tenuiflorus W. Curtis


Carduus tenuiflorus is an herbaceous winter annual or biennial that invades disturbed areas. The most serious infestations occur in the Pacific coastal states, but Carduus tenuiflorus also occurs sporadically in the eastern United States. Plants grow up to 6 ft. (1.8 m) tall with single or multiple spiny stems with wings arising from the base of the spines.
Stem wings can be up to 0.4 in. (10 mm) wide. Leaves are deeply lobed and also very spiny.
The small flower heads (less than 1 in. [2.5 cm] long) are slender, purple, and lack stalks. Flowering occurs from May to July.
Fruit has a dry outer coating and is 0.16-0.20 in. (4-5 mm) long.
Ecological Threat
Carduus tenuiflorus invades pastures, old fields, vacant lots, and other disturbed areas. Its presence reduces the forage productivity of pastures. It is native to Europe and was recognized as a serious invader in the western United States as early as 1956.

Selected Images


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

State Regulated List

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

Taxonomic Rank

Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteridae
Order: Asterales
Family: Asteraceae
Genus: Carduus
Subject: Carduus tenuiflorus W. Curtis

Synonyms and Other Names

Other Common Names:
Italian thistle, winged plumeless thistle


Plants - Forbs/Herbs