Rhaponticum repens (Russian Knapweed) - photos and description

 

 


Bracts imbricate, green with papery, translucent margins.


Roots are black.


Lower leaves in above photo.


Upper leaves in above photo.

General: Perennial plant branching near the base giving it a bushy growth habit. Stems are leafy, angled, and tomentose. The plant has creeping roots that are black in colour, and scaly. Designated a noxious weed in Saskatchewan. The species name of repens means 'creeping'.

Flowers: Flowers are many, terminal, discoid, pinkish-purple. We measured a flower head to 15 mm diameter and the involucre to 10 mm tall. The outer and middle bracts are ovate, with a broad, papery, translucent margin. The innermost bracts narrow to a plumose-hairy tip.

Leaves: The lower are alternate, lanceolate to oblong, irregularly toothed to pinnately lobed; we measured a lower leaf at 74 mm long by 19 mm wide. The upper leaves are sessile, entire, oblong; we measured an upper leaf at 27 mm long by 5 mm wide. Leaves are glandular-punctate.

Height: Height is listed in Budd's Flora to 100 cm, we measured plants to 71 cm tall.

Habitat: Fields, pastures roadsides, waste ground.

Abundance: Fairly common.

Origin: Introduced.

Synonyms: Listed in some of the field guides we use as Centaurea repens, Acroptilon repens.

When and where photographed: Took the above photos July 20th in an old gravel pit now a pasture, about 400 km west of our home in Regina, SK.