Centaurea stoebe (Spotted Knapweed) - photos and description

Small plant in above photo.

Rarely plants have white flowers.

Bracts have vertical stripes, black tips, tuft of hairs on the tip.

Spent flower head, bracts have vertical stripes, black tips, tuft of hairs on the tip.




1st year basal rosette of leaves.

Basal leaf in above photo.

Stem leaf in above photo

Leaves with tiny pits on top surface.

General: Upright biennual branching above the base. First year growth a basal rosette of leaves. Stems angled, rough hairy with matted hairs. Foliage greyish-green. 

Has been designated a prohibited weed in Saskatchewan.

Flowers: Flower heads grow singly on the end of stems. Outer ray florets divided into 4 or 5 threadlike segments, outer rays sterile. Disk florets are fertile. Ray and disk florets pink in colour. We measured a large flower head at 41 mm diameter, more typically were 30-35 mm diameter. Involucre bracts imbricate (overlapping as shingles on a roof), striate, with a black tip, the tips of the bracts with a fringe of hairs. We measured an involucre at 7 mm diameter, and 10 mm tall.

Leaves: Leaves are alternate, basal and lower stem leaves pinnatifid, top leaves entire. We  measured a basal leaf at 23 cm long (including petiole) and 7.5 cm wide. Leaves punctate, rough hairy.

Height: Height in Budd's Flora is listed to 100 cm, we measured plants to 79 cm tall.

Habitat: Waste ground and roadsides.

Abundance: Uncommon.

Origin: Introduced.

Synonym: Listed in some of the field guides we use as Centaurea maculosa.

When and where photographed: These photos were taken July 15th and July 20th, waste ground in the north end of Regina, SK.