slenderflower thistle
(Carduus tenuiflorus)
Overview
- Appearance
- 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.
- Foliage
- Stem wings can be up to 0.4 in. (10 mm) wide. Leaves are deeply lobed and also very spiny.
- Flowers
- 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
- 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
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 List - This map identifies those states that list this species on their invasive species list or law. For more information, visit Invasive.org
Invasive Listing Sources
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