Carduus acanthoides - Asteraceae Family - Biennial
- Flowers: Flower heads are red-purple in color and can span up to 1 inch. Flower stems are branching with spiny wings extending to the flower head.
- Seeds: Seeds are oblong, striated, and slightly curved. They are mainly wind-dispersed and can remain viable in the soil for up to 10 years. Plumeless Thistle spreads entirely by seed.
- Leaves: The leaves of the basal rosette are 4-8 inches long and have spiny teeth. The stem leaves are alternate and attach directly to the stem. They are sparsely hairy underneath.
- Flowering Time: June through August.
- Life cycle: Plumeless Thistle is a biennial, meaning it produces a basal rosette in its first season with the stems and flowering bodies coming the season after. It flowers and disperses seeds from early to mid-summer.
- Plumeless Thistle is unpalatable to livestock and can greatly reduce an area’s forage potential if allowed to spread.
- Thistle fragments and spines may injure livestock and humans moving through infestations.
- Dense stands of thistles can greatly impede recreational activities, hinder grazing livestock, and obstruct wildlife from access to water.
- Plumeless Thistle forms thick monocultures which can greatly reduce the biodiversity in an area.
Most effective control methods
- Prior to flowering, small infestations can be effectively controlled by hand pulling or digging while being careful to ensure the removal of the entire root system. Mowing and cutting plants can also be effective if done prior to seed production.
- Several herbicides are useful for managing this weed, if applied in the fall when the plants are in their seedling or rosette stage.
Plumeless thistle: flower
Plumeless thistle: rosette
Plumeless thistle: foliage and flower
Plumeless thistle: stem and foliage
Plumeless thistle: seeds
Plumeless thistle: infestation
Agriculture Victoria. (2016, June 20). Plumeless thistle (Carduus acanthoides). Retrieved from http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/weeds_plumeless-thistle
Colorado State University. (2015, July). Plumeless thistle identification and management [PDF file]. Retrieved from https://drive.google.com/file/d/14vAswiwCYXTteghJap7pFPJM9tWL3-1g/view View PDF
Colorado Weed Management Association and the Center for Invasive Species and Ecosystem Health. Spiny plumeless thistle (Carduus acanthoides). Retrieved from https://www.misin.msu.edu/facts/detail/?project=&id=212&cname=Spiny-plumeless-thistle
Minnesota Department of Agriculture. Prohibited – control noxious weed: Plumeless thistle – carduus acanthoides L. Retrieved from https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/plumelessthistle
Moechnig, M. (2016, April 8). Plumeless thistle (Carduus acanthoides). Retrieved from https://wiki.bugwood.org/HPIPM:Plumeless_thistle
University of Nebraska – Lincoln Extension. (2010, January). Plumeless thistle [PDF file]. Retrieved from http://www.neweed.org/NeWeeds/plumeless.pdf View PDF