Yellow starthistle - Centaurea solstitialis. Growth Form/Reproduction: Winter annual. 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. Origin: Europe. Spotted knapweed, Centaurea stoebe spp. Seed. 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. 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. Genetics Yellow starthistle is diploid (2n=16), with a large amount of genetic variation (Sun, 1997; Sun and Ritland, 1998). Centaurea solstitialis Photo courtesy Bob Case. In deep-soiled rangelands Yellow Starthistle roots grow fast and deep (Sheley and Petroff 1999). yellow star-thistle in the bolting stage but, before the flower’s spines develop. PREVENT Centaurea solstitalis Family: Asteraceae (Sunflower). Other Common Names: St. Barnaby’s thistle, yellow cockspur. Yellow star-thistle is a listed noxious weed and is invasive in many western states. 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. It has taken over vast areas of land in the western United States with estimates of over 15 million acres in California, 280,000 acres in Idaho, and 135,000 acres in Oregon. Dense populations of this plant result in lowered yield and quality of forages and occasionally crops. 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). Common names: yellow starthistle Centaurea solstitialis (yellow starthistle) is a bushy winter annual (family Asteraceae) that invades 12 million acres in California. Goats will eat the plant even in the spiny stages. Sometimes it can grow in clusters that appear shrubby. Yellow starthistle, Centaurea solstitialis, is a particularly nasty type of invasive knapweed in the Aster family. It is easily recognizable from its brilliant yellow flowers, and cactus like spines. Adults overwinter outside the host plant, leaving their … Weed Seed - Yellow Starthistle (Centaurea solstitialis) Plant pest card - Yellow starthistle. Yellow starthistle is an invasive plant found in pastures and rangelands. 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. Grazing reduces biomass and seed produc-tion. However, Yellow Starthistle growth rates can decline as its density increases. It is poisonous to horses. Invasive plants should never be considered as forage. 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). Adults cause minor defoliation, with the majority of the damage caused by larval feeding. ... For more details check out the Invasive Species Compendium datasheet on Centaurea solstitialis (yellow starthistle). 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