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Bull Thistle

Cirsium vulgare L.

Asteraceae (Aster Family)

▲▼ first year rosettes

▲▼ first year rosettes

▲▼ first year rosettes

 

▲ green, not whitish, leaf underside

▲▼ early second year plant

▲▼ elongating stems with flower buds in second-year growth

▲▼ elongating stems with flower buds in second-year growth

▲▼ stems and leaves

▲▼ mature, flowering plants

▲▼ mature, flowering plants

▲▼mature, flowering plants

▲▼ mature, flowering plants in Minnesota (over 8 feet tall)

▲ mature, flowering plants, with Bob 

▲▼ inflorescences showing green, rounded, pointed, bracts and cobwebby hairs at base of  bracts

 

 

▲▼ seed/fruit leaving inflorescences

 

 

Cirsium vulgare (Savi) Ten., Bull Thistle: (Bayer Code:  CIRVU; US Code CIVU)

·         European native, invasive biennial weed fairly common in Midwest, including Missouri

·         First year produces rosettes of green leaves (purplish in winter), that are lanceolate in outline, covered in transparent, outspread hairs, and deeply-lobed with spine-tipped lobs

·         Second year, usually produces a single stem 2-7 feet tall from the base that has much branching in the upper portions

·         Leaves often deeply lobed with upper leaf surfaces with stiff bristles on surfaces and on margins

·         Leaf undersides greenish, hairy, and leaf bases extend down the stem to produce spiny, leafy “wings” along the stem

·         Flower heads are 1-2 inch diameter, with purplish pink ray flowers, blooming in summer (June-September)

·         Base of inflorescence is urn-shaped, and bracts at base of flower bend away from the base of the receptacle to form very slender, almost cylindrical green spines; cobwebby hairs fill in between the green spines

·         Two native thistles have somewhat similar growth habit and flower shapes and colors:

      o   Tall Thistle (Cirsium altissimum) a native thistle that has white leaf undersides and may have unlobed or lobed leaves in both first-year rosettes and along the upright stems, and the head bracts hug the base of the head, except for the spiny tip, which bends out from the head base

      o   Field Thistle (Cirsium discolor) a native thistle that has white leaf undersides, and the stems lack leafy wings and the head bracts hug the base of the head, except for the spiny tip, which bends out from the head base

 

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