Yellow starthistle


Annual (occasionally biennial) that infests disturbed areas such as roadsides and open fields, as well as rangelands, grasslands, open woodlands, pastures, and crop fields. Yellow starthistle is toxic to horses if consumed.
Also Known As: Golden starthistle, yellow cockspur,
St. Barnaby’s thistle
Stems/Leaves: Stiff, wiry stems (1-6 ft tall) are often branched; leaves (1.5-6 in. long) are blue- to gray-green, densely covered with fine, cotton-like hairs, alternate, linear to oblong in shape with smooth, toothed, or lobed margins; leaf bases extend down the stem creating wings (up to 0.2 in. wide)
Flowers: Flower heads (0.5-1.5 in. diameter) found singly at stem ends, oval or round with a yellow flower; several stiff, sharp, straw colored bracts (0.75 in. long) are found beneath the flower
Roots: Taproot
Reproduction: Seed; successful management prevents seed production/spread
Management Do’s and Don’ts
• Prevention and maintenance of a healthy plant community are the best management methods
• Frequent cultivation is effective
• Mow plants in late bud or early bloom to reduce
seed production
• Burning is effective if done before seed production
• Numerous effective biological control agents have been introduced
• Herbicides are effective


Malta starthisle


African rue


Annual (occasionally biennial) that infests disturbed areas such as roadsides and open fields, as well as rangelands, grasslands, open woodlands, pastures, and crop fields.
Also Known As: Tocolote, Maltese starthistle
Stems/Leaves: Stiff, wiry stems (1-3 ft tall) often branched; leaves (0.8-6 in. long) are green to blue-green, covered with fine hairs; basal leaves are oval to linear, entire to lobed margins; stem leaves are narrow, entire to wavy margins, with bases that extend down the stem creating wings (0.12 in. wide)
Flowers: Flower heads (0.4-0.8 in. diameter) found singly or in groups of 2-3 at ends of stems, oval in
shape, with yellow flowers; stiff purple or brown bracts
(0.2-0.6 in. long) are found beneath flowers
Roots: Taproot
Reproduction: Seed; successful management prevents seed production/spread
Management Do’s and Don’ts
• Prevention and early detection are the most effective control methods
• Frequent cultivation is effective
• Mow plants in late bud or early bloom to reduce
seed production
• Burning is effective if done before seed production
• Herbicides are effective


Annual (occasionally biennial) that infests disturbed areas such as roadsides and open fields, as well as rangelands, grasslands, open woodlands, pastures, and crop fields.

Also Known As: Tocolote, Maltese starthistle
Stems/Leaves: Stiff, wiry stems (1-3 ft tall) often branched; leaves (0.8-6 in. long) are green to blue-green, covered with fine hairs; basal leaves are oval to linear, entire to lobed margins; stem leaves are narrow, entire to wavy margins, with bases that extend down the stem creating wings (0.12 in. wide)
Flowers: Flower heads (0.4-0.8 in. diameter) found singly or in groups of 2-3 at ends of stems, oval in
shape, with yellow flowers; stiff purple or brown bracts
(0.2-0.6 in. long) are found beneath flowers
Roots: Taproot
Reproduction: Seed; successful management prevents seed production/spread
Management Do’s and Don’ts
• Prevention and early detection are the most effective control methods
• Frequent cultivation is effective
• Mow plants in late bud or early bloom to reduce
seed production
• Burning is effective if done before seed production
• Herbicides are effective

Purple starthistle


Annual to perennial that infests open fields, roadsides, grasslands, rangelands, and especially disturbed areas; also found in fertile or alluvial soils.
Also Known As:Red starthistle
Stems/Leaves: Numerous, highly branched stems (up to
4 ft tall); plants may form clumps or bushes; leaves
(4-8 in. long) alternate, covered with long, wooly hairs; lower leaves deeply lobed; upper leaves pinnate-divided with narrow leaflets, DO NOT form wings on upper stems
Flowers: Oval shaped flower heads (0.75-1 in. long) borne on leafy stems; flowers are deep purple to lavender; below flowers are several stiff, straw-colored spines
(0.4-1 in. long)
Roots: Taproot
Reproduction: Seed; successful management prevents seed production/spread
Management Do’s and Don’ts
• Physical removal before seed production
for single plants/small infestations
• Herbicides are effective
• DO NOT MOW