Pink, Rose, Red, or Purple Flowered Forbs

 

Russian Knapweed
Acroptilon repens (L.) DC (Aster family, Asteraceae)
 

Description

Multi-stemmed perennial forb, 9 to 39 inches tall; openly branched stems covered with cobwebby, matted hairs; creeping rhizomes scaly, dark brown to black; root system branches frequently with individual roots reaching 25 feet in depth; stems with numerous branches; Russian knapweed is similar in appearance to other knapweeds and star-thistles; however, Russian knapweed has rounded to pointed membranous margins whereas flower head bracts of other knapweeds and star-thistles are tipped or fringed with short spines.

Leaves: Basal and cauline (along the stem), simple, alternate; upper cauline leaves narrowly lanceolate to linear, 1/8 to 1/2 inch long, margins entire or toothed; lower cauline leaves often serrate; basal leaves lobed and gray pubescent.

Flowers: Flowers June to September; pink to purplish flower heads range from one to numerous, rising at the end of branches, arranged in a flat-topped to panicle-like inflorescence; flower head bracts arranged in 6 to 8 rows.

Fruits: Oblong achene (fruit), 1/8 to 1/4 inch long; deciduous pappus (tuft-like appendage) at end of achene, whitish bristles unequal, 1/8 to 3/8 inch long, barbed toward the base, feathery toward the tip.

Habitat

Cultivated areas and disturbed or degraded sites in meadows, grassland and riparian communities, and roadsides; establishes in many soil types within elevations that generally range from 3,000 to 8,000 feet.

Propagation/Phenology

Reproduces primarily by vegetative shoots from rhizomes although individual plants can produce small quantities of viable seed. Seed can remain viable 2 to 3 years. Severed roots can produce new shoots from a depth of up to 6 inches.

Comments

Native to central Asia; Russian knapweed is a very competitive and aggressive plant with allelopathic effects; stands may persist indefinitely once established. Arizona prohibited/restricted noxious weed and New Mexico Class B noxious weed.

Collage of images of Russian thistle

 

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Forest Service Shield
Invasive plants and weeds of the national forests and grasslands in the southwestern region
Russian knapweed flower heads and foliage Russian knapweed flower heads Russian knapweed foliage Russian knapweed plants