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


Purple Starthistle
Centaurea calcitrapa L. (Aster family, Asteraceae)


Multi-branched annual, biennial or perennial forb; 3 feet 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/summer.

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 densely covered with gray hairs.

Flowers: Flowers July to October; 1/4 to 3/8 inch diameter flower heads solitary or several with 25 to 40 purple flowers per head, 5/8 to 1 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, 3/8 to 1 inch long.

Fruit: White achenes oblong, 1/8 to 3/16 inch long, often brown streaked, apex flattened and tapered to a rounded, laterally notched base, often brown-streaked; pappus usually lacking.


Cultivated and disturbed or degraded fertile soil sites in meadows, grassland, woodland, and forest communities, and roadsides within elevations that generally range from 3,300 to 8,000 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 southern Europe; purple starthistle is a very competitive and aggressive plant with allelopathic effects; stands of purple starthistle may persist indefinitely once established. Arizona

Collage of 4 images of Purple starthistle


Forest Service Shield
Invasive plants and weeds of the national forests and grasslands in the southwestern region
Purple starthistle flower head Purple starthistle flower head spines Purple starthistle plants Purple starthistle basal rosette