Pink, Rose, Red, or Purple Flowered Forbs

Pink, Rose, Red & Purple Flowered Forbs
Alfalfa
Black henbane
Blue Mustard
Bull thistle
Canada thistle
Common burdock
Diffuse knapweed
Hounds-tongue
Iberian knapweed
Meadow knapweed
Musk thistle
Purple loosestrife
Purple starthistle
Red clover
Redstem filaree
Russian knapweed
Scotch thistle
Spiny plumeless thistle
Spotted knapweed
Squarrose knapweed
Tall morning-glory
Teasel

 

Spiny Plumeless Thistle
Onopordum acanthium L. (Aster family, Asteraceae)
 

Description

Multi-stemmed biennial (or winter annual) forb to 5 feet tall; openly branched stems erect, spiny-winged from leaf bases; taprooted; plants exist as basal rosettes until flowering shoots develop at maturity.

Leaves: Basal leaves opposite, elliptic to lanceolate, pinnately lobed, with prickly-toothed margins; stem leaves alternate, with bases that extend down the stem forming spiny wings (decurrent); stems strongly winged, glabrous to lightly woolly; leaves 1-pinnate lobed, typically sparsely hairy, lower leaves mostly 4 to 8 inches long.

Flowers: Flowers May to August; purple flower heads spherical 3/8 to 1-1/8 inches in diameter, one to numerous on stalks less than 3/4 inch long; flower head bracts glabrous to pubescent, tips erect to spreading; flower head receptacles flat, densely covered with cream- colored bristles.

Fruits: Glossy golden to brown achenes elliptic, less than 1/8 inch long; curved, slightly compressed; cream-colored, 3/8 to 1/2 inch long, pappus bristles are numerous; united at the base to form a ring and are deciduous as a unit.

Habitat

Dry, well drained, cultivated and disturbed or degraded sites in meadows, grassland, chaparral, woodland, forest, and riparian communities, and roadsides within elevations that generally range from 4,200 to 8,800 feet.

Propagation/Phenology

Reproduces by seed; seeds appear to lack an after ripening period. Seeds typically germinate late summer through spring, depending on environmental conditions. Seeds can germinate in constant heavy shade, but seedlings seldom reach maturity under this condition; additionally, viable seeds rarely persist in the soil seed bank due to decomposition and seed predation by insects, mammals, and birds.

Comments

Native to Europe; serious infestations are often associated with sandy, fertile soils; this species and musk thistle readily hybridize with one another, and plants with intermediate characteristics may be found where their ranges overlap. Arizona prohibited noxious weed.

Collage of images of Spiny Plumeless Thistle

 

Forest Service Shield
Invasive plants and weeds of the national forests and grasslands in the southwestern region
Spiny plumeless thistle flower heads, winged stems, and foliage Spiny plumeless thistle flower heads Spiny plumeless thistle bascal rosette Spiny plumeless thistle plants