Centaurea maculosa, Centaurea stoebe, spotted knapweed, star thistle
Description: biennial or perennial
Place of origin: Eastern Europe
Urban habitat: commonly found in dry, disturbed sites, vacant lots, along roadways and railroad tracks; tolerates dry, compacted soil.
Ecological function: disturbance-adapted colonizer of bare ground; food and habitat for wildlife; erosion control on slopes
History: Centaurea biebersteinii was introduced into North America by accident, most likely as a contaminant in alfalfa seed and/or in ships’ ballast in the late 1800’s. The plant is considered an invasive species in the U.S. and Canada, primarily due to its ability to suppress the growth of nearby plants with its production of allelopathic chemicals that act as herbicides. Its hard seed coat allows it to remain viable in soil for up to 10 years. Although it is said to be bitter in taste and not a preferred foraging plant for mammalian herbivores, its leaves and flower heads have a relatively high nutritional value. Centaurea biebersteinii contains a compound with antimicrobial properties and has proven to be active against some human carcinoma cells.