Bull Thistle

Bull thistle (Cirsium vulgare) is a robust biennial weed recognized by its fiercely spiny foliage and showy purple flower heads. In its first year it forms a low rosette, and in its second year it bolts into a tall, branching flowering stalk before dying.

Native to Eurasia and North Africa, it has spread widely as a weed of pastures, roadsides, and disturbed land. While considered a noxious weed in many places, its flowers are highly attractive to bees and butterflies.

Unmistakable for its spines and large purple blooms.

• Leaves: Deeply lobed, coarse, with sharp spines on the margins and stiff, prickly hairs on the upper surface
• Stems: Erect, branched, with spiny wings running along them
• Flowers: Large, rose-purple flower heads (1-2 inches across) cupped by spiny, flask-shaped bracts
• Size: Up to 3-6 feet tall in its flowering year
• Seeds: Topped with feathery, off-white pappus for wind dispersal

Not cultivated; included for management.

• Light: Full sun
• Water: Drought-tolerant; thrives in dry, disturbed soils
• Soil: Adapts to most soils; common in overgrazed or disturbed ground
• Temperature: Hardy biennial across a broad climate range
• Control: Dig or cut the taproot below the crown before it flowers; mow or remove flower heads to prevent prolific wind-borne seed
• Life cycle: Biennial, flowering and dying in its second year

Bull thistle is native to Europe, western Asia, and North Africa but has naturalized across North America, Australia, and other temperate regions, where it is often listed as a noxious or invasive weed.

It colonizes pastures, roadsides, fields, clearcuts, and disturbed land, especially in sunny, open sites with bare soil.