Appearance
Centaurea stoebe ssp. micranthos is an herbaceous biennial or perennial plant that readily invades open areas. Its name is derived from the black margins of the flower bract tips which give the flower heads a spotted look.
Foliage
A basal rosette of deeply lobed leaves is produced the first year. Rosette leaves are deeply lobed, petiolate, and approximately 8 in. (20 cm) long. Flowering stems are 1-4 ft. (0.3-1.2 m) tall and branched. Stem leaves are alternate and may be slightly lobed or linear. Leaves become smaller and less lobed toward the apex.
Flowers
The small purple to pink flowers bloom in the early summer.
Fruit
Mature seeds are shiny black and produced in erect, slender green pods which turn pale brown when mature. The copious seeds are distributed by the wind and contaminated hay.
Ecological Threat
Centaurea stoebe ssp. micranthos invades a wide variety of habitats including pastures, open forests, prairies, meadows, old fields, and disturbed areas. It displaces native vegetation and reduces the forage potential for wildlife and livestock. It is native to Europe and western Asia. It was accidentally introduced into North America in contaminated alfalfa and clover seed in the late 1800s.