Bull Thistle
Cirsium vulgare · None (Herbaceous Biennial)
Plant Family
Asteraceae
Tree Category
Invasive Weed / Flowering Herb
Variety / Cultivar
None
Hardiness Zones
USDA Zones 3 through 10.
About This Tree
While not a tree, it is an upright herbaceous plant. It forms a tall, erect stem with spiny wings and large, globe-shaped purple flower heads atop prickly greenish-gray involucres.
Leaf Characteristics
Deeply lobed, lance-shaped leaves with stiff, needle-like spines at the tips of the lobes. Dark green and hairy on top, lighter and woolly underneath.
Bark Characteristics
Not applicable. The stem is green, stout, and features prominent prickly wings extending down from the leaf bases.
Growing Information
Origin Region
Native to Europe, Western Asia, and Northern Africa; widely naturalized in North America.
Growing Season
Biennial cycle. First year forms a basal rosette; second year it bolts, flowers in mid-to-late summer, and sets seed in fall.
Sunlight & Water Needs
Full sun; adaptable to various soil moistures but thrives in well-drained, disturbed areas. High drought tolerance.
Mature Size
Height: 3 to 6 feet; Spread: 1 to 2 feet; Growth rate: Rapid bolting in year two.
Special Characteristics
Highly invasive and noxious weed in many regions. Recognized by its formidable spines and vibrant purple pom-pom-like flowers. High seed production.
Wildlife & Ecology
Highly attractive to pollinators like bumblebees and butterflies. Seeds are a food source for goldfinches. Can be a nuisance to livestock due to prickles.