Pink, Rose, Red, or Purple Flowered Forbs

Pink, Rose, Red & Purple Flowered Forbs
Black henbane
Blue Mustard
Bull thistle
Canada thistle
Common burdock
Diffuse knapweed
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


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


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.


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


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.


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