Genetics Yellow starthistle is diploid (2n=16), with a large amount of genetic variation (Sun, 1997; Sun and Ritland, 1998). Adults overwinter outside the host plant, leaving their … Yellow starthistle is in the Asteraceae family and is a long-lived winter annual; Stems are erect, rough, branching and can grow up to 1 m in height. Yellow Starthistle Centaurea solstitialis L. Sunflower family (Asteraceae) NATIVE RANGE Africa, temperate Asia and Eurasia (Balkan-Asia Minor, the Middle East and south-central Europe) Mediterranean region of southern Europe and northern Africa, especially Turkey DESCRIPTION Yellow starthistle is an annual herbaceous plant. Bangasternus orientalis, or the yellow starthistle bud weevil, reduces seed production of yellow starthistle plants by 50 to 60%. yellow star-thistle in the bolting stage but, before the flower’s spines develop. Legal Status Central Kootenay: Weed Control Act, Forest and Range Practices Act, Community Charters Act. Invasive Plant Species of West Virginia Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007 John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995. Perennial grasses can compete against yellow starthistle invasions, particularly species that can initiate growth in the fall. However, Yellow Starthistle growth rates can decline as its density increases. Yellow starthistle is an invasive plant found in pastures and rangelands. Yellow starthistle - Centaurea solstitialis. Overgrazing will reduce the ability of other vegetation to recover and shade out the starthistle. It is poisonous to horses. Yellow starthistle, Centaurea solstitialis, is a particularly nasty type of invasive knapweed in the Aster family. Yellow starthistle is an invasive herbaceous annual or biennial of the Asteraceae family that spreads by seeds, forming dense stands in open, sunny areas (Maddox, 1981). Other Common Names: St. Barnaby’s thistle, yellow cockspur. Spotted knapweed, Centaurea stoebe spp. Weed Seed - Yellow Starthistle (Centaurea solstitialis) Plant pest card - Yellow starthistle. Grazing reduces biomass and seed produc-tion. Yellow star-thistle is a listed noxious weed and is invasive in many western states. Yellow starthistle inhabits open hills, grasslands, open woodlands, fields, roadsides, and rangelands, and it is considered one of the most serious rangeland weeds in the state. Centaurea solstitialis Photo courtesy Bob Case. PREVENT Centaurea solstitalis Family: Asteraceae (Sunflower). Common names: yellow starthistle Centaurea solstitialis (yellow starthistle) is a bushy winter annual (family Asteraceae) that invades 12 million acres in California. Adults cause minor defoliation, with the majority of the damage caused by larval feeding. Sometimes it can grow in clusters that appear shrubby. Impacts:Agricultural: Infestations can reduce forage quality and forage availability in pastures and in hay. Growth Form/Reproduction: Winter annual. Goats will eat the plant even in the spiny stages. ... For more details check out the Invasive Species Compendium datasheet on Centaurea solstitialis (yellow starthistle). Consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g., threatened or endangered species, state noxious status, and wetland indicator values). Seed. In deep-soiled rangelands Yellow Starthistle roots grow fast and deep (Sheley and Petroff 1999). micranthos (invasive), diffuse knapweed, Centaurea diffusa (invasive), meadow knapweed, Centaurea x moncktonii (invasive), and brown knapweed, Centaurea jacea (invasive) – These knapweeds have pink or white flowers, unlike the yellow flowers of yellow starthistle and they lack the one inch long spines on their flowering heads that yellow starthistle has. 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