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

 

Diffuse Knapweed
Centaurea diffusa Lam. (Aster family, Asteraceae)
 

Description

Multi-branched annual or perennial forb, 4 to 31-1/2 inches tall, with spiny or comb-like flower head bracts; long taprooted plants exist as basal rosettes until erect, highly branched flowering stems are produced in late spring/summer.

Leaves: Cotyledons spatulate to oval; rosette leaves pinnate- divided without straw-colored spines at the centers of rosettes; leaves alternate, resin-dotted; lower stem leaves deeply 1 to 2 pinnate-lobed, 4 to 8 inches long; upper stem leaves wingless, entire, linear or bract-like 3/8 to 3/4 inch long. Foliage variously covered with short to medium interwoven gray hairs.

Flowers: Flowers June to September; 1/4 to 3/8 inch diameter flower heads solitary or several with 12 to 13 white, pink, or pale purple flowers per head, 1/2 inch long; greenish or straw-colored flower head bracts overlapping in several rows, 3/8 to 1/2 inch long, tips variously spiny or comb-like, central spine spreading, 1/8 inch long.

Fruit: Dark brown achenes oblong, 1/8 to 3/16 inch long, apex flattened and tapered to a rounded, laterally notched base, roughly 13 per head, pappus scales less than 1/16 inch long or lacking.

Habitat

Cultivated and disturbed or degraded well-drained soil sites in meadows, grassland, woodland, and forest communities, and roadsides within elevations that generally range below 7,200 feet.

Propagation/Phenology

Reproduces by seed, up to 40,000 per plant; germination occurs over a broad range of environmental conditions; seeds exhibit three germination patterns: nondormant seeds that germinate with or without light exposure, dormant seeds that germinate in response to red light, and dormant seeds that are not light sensitive.

Comments

Native to southern Europe; diffuse knapweed is a very competitive and aggressive plant with allelopathic effects; stands of diffuse knapweed may persist indefinitely once established. Arizona prohibited/ restricted noxious weed and New Mexico Class A noxious weed.

Collage of 4 images of Diffuse Knapweed

 

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