Yellow Starthistle
Centaurea solstitialis

Yellow Starthistle adult
Yellow starthistle is a two to three foot tall winter annual with blue-green coloration.
Yellow Starthistle rosette
Rosette leaves are deeply lobed and could be confused with dandelion.
Weed Infestation
Yellow Starthistle infestation
Yellow starthistle was introduced from Europe. It grows well on dry sites in rangeland, roadsides, and waste areas. It can cause "Chewing disease" in horses that consume it.
Yellow Starthistle flower
Flowers are yellow. Cream-colored thorns, one-quarter to three-quarter inches long, protrude from the flowering heads. Bloom is in early summer.
Winged Stem
Yellow Starthistle stem
Stems are sparsely leaved and heavily ridged.
Tap Root
Yellow Starthistle root