: St. Barnaby's thistle, yellow star-thistle
: Introduced to the United States in contaminated alfalfa seed.
: Pubescent winter annual. or rarely a biennial or short-lived perennial forb.
: Produces rosette leaves that lie close to the ground; lower leaves are 2-6 in. long, progressively smaller up the stem. Upper leaves are 0.4-1.2 in. long, narrow, and densely covered in cobwebby hairs late in the season.
: Stiff, erect, 6-72 in. in height; openly branched.
: Inflorescences borne in solitary flowerheads on stem tips; involucre 0.5-0.7 in. long, phyllaries have 1 long central spine (0.4-1 in. long) and 2 more pairs of short lateral spines densely covered with hairs.
Fruit and seeds
: Achenes of 2 types, both glabrous and 2-3 mm. long. Most seeds have short, 2-5 mm., stiff pappus (plumed). Periphery seeds are darker in color with no pappus.
: Native to southern Europe and western Eurasia. Can be found in disturbed sites such as deserts, high mountain and moist coastal sites.
: By wind dispersed seeds.
Monitoring and rapid response
: Responds to integrated pest management programs. Hand-pulling, hoeing or weed whipping can be effective for small populations. Mowing can reduce density, but mowing heights must be set correctly and mowings must be timed. Herbicides along are not recommended and six natural insect enemies have been implemented.
: The information provided in this factsheet was gathered from CABI: Invasive Species Compendium and US Forest Service FEIS: CENSOL
Individual species images that appear with a number in a black box are courtesy of the Bugwood.org network (http://www.invasive.org). Individual photo author credits may not be included due to the small display size of the images and subsequent difficulty of reading the provided text. All other images appear courtesy of Google (http://images.google.com).