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

 

Iberian Knapweed
Centaurea iberica Trevir. ex Spreng. (Aster family, Asteraceae)
 

Description

Multi-branched perennial forb, 39 inches tall, with spiny or comb- like flower head bracts; stoutly taprooted; plants exist as basal rosettes until erect, highly branched flowering stems are produced in late spring.
Leaves: Cotyledons spatulate to oval; rosette leaves pinnate- divided with straw-colored spines at their centers; leaves alternate, resin-dotted, lower stem leaves deeply 1 to 2 pinnate-lobed, 4 to 8 inches long; upper stem leaves wingless, mostly pinnate-divided, 3/8 to 3/4 inch long. Foliage variously covered with short to medium interwoven gray hairs; new leaves green and covered with minute bristly hairs.

Flowers: Flowers July to October; 1/4 to 1/2 inch diameter flower heads solitary or several with 12 to 13 rose-pink to whitish flowers per head, 5/8 to 3/4 inch long; greenish or straw-colored flower head bracts overlapping in several rows, 5/8 to 3/4 inch long, tips variously spiny or comb-like; central spine stout or spreading, 3/8 to 1 inch long.

Fruit: Whitish achenes oblong, 1/8 to 3/16 inch long, often brown streaked, apex flattened and tapered to a rounded, laterally notched base; pappus scales less than 1/16 inch long.

Habitat

Often colonizes banks of watercourses and other moist sites within elevations that generally range below 3,200 feet.

Propagation/Phenology

Reproduces by seed, up to 40,000 per plant; germination occurs over a broad range of environmental conditions; plants produce fewer viable seeds in dry years; infestation density correlates with the age
of the population and degree of disturbance; plants seldom persist in shaded places.

Comments

Native to southeast Eurasia; Iberian knapweed is a very competitive and aggressive plant with allelopathic effects; stands of Iberian knapweed may persist indefinitely once established; old flower stems can persist after senescence; flower head bracts and achenes remaining on old stems can aid with species identification when plants are overwintering as rosettes. Arizona prohibited noxious weed.

Collage of 4 images of Iberian knapweed

 

 
Forest Service Shield
Invasive plants and weeds of the national forests and grasslands in the southwestern region
Iberian knapweed pre-bloom flower head Iberian knapweed basal rosettes Iberian knapweed flower heads Iberian knapweed flower head