General: Yellow Star-thistle (Centaurea solstitialis) is an annual forb with basal leaves and a main flowering stalk that branches into many stalks that grow to shin or knee high. The flower buds are well armored with nasty, 3/4-inch-long spines. The flowers are yellow and emerge from the top of the flower bud. Yellow and Malta Star-thistles both have yellow flowers, but Yellow Star-thistles have long, straw-colored spines (about 3/4 inch) without with lateral spines.

Yellow Star-thistle is a nasty, invasive noxious weed that is becoming a more common component of disturbed semi-desert vegetation in California. Around Las Vegas, this species is not present -- let's all work to make sure it stays that way. Look for this species in town and in disturbed roadsides and open fields.

This is a noxious weed. If hikers and other visitors to the native habitats around Las Vegas see this species, please report the observation to the Nevada Department of Agriculture using their online forms. If you have this species on your private property, please consider eradicating it.

Family: Sunflower (Asteraceae).

Other Names: Yellow Starthistle.

Plant Form: Basal leaves with upright flower stalk. Nasty spines.

Height: To about 2 feet.

Stems: A single stalk forks to produce several flowering stalks.

Leaves: Generally basal, generally narrow and lobed, spiny. Upper leaves reduced

Flowers: Blooms during early spring. Flowers grow at the top of the flower stalks; petals many, yellow.

Seeds: Tiny, many per plant.

Habitat: Roadsides, disturbed sites, pastures.

Elevation: To about 4,000 feet; usually lower elevations.

Distribution: Established throughout the U.S. and southern Canada. Native to southern Europe.

Comments: Can be toxic to horses.