Native to Europe and western Asia, spotted knapweed is a herbaceous biennial or perennial weed in the Asteraceae (aster) family. In many parts of the US, primarily in the northwest and north central regions, it is regarded as invasive. The plant can be found in many open, disturbed places, including stream banks, pond shorelines, sand prairies, abandoned fields and pastures, roadside ditches, and railroad tracks. It eliminates natural species and cattle fodder. The flower heads have a speckled appearance due to the bract tips’ black borders, which are a vivid lavender color and the source of the plant’s popular name. Under a basal rosette of deeply lobed leaves covered in fine, short hairs, it typically has a strong taproot. In a single growth season, up to 6 erect stems that can reach a height of 3 feet can arise from the same root crown.
Ecological Impact
Currently a typical component of mangrove ecosystems and beaches with little wave movement; occasionally develops forests of seedlings near the high-tide line. reported from natural regions in the counties of Monroe, Dade, Collier, Lee, Palm Beach, and Martin, including Everglades National Park. Category I invasive species according to the Florida Exotic Pest Plant Council (FLEPPC).
Management Strategies
Landscape seedlings are manually removed.
Soil
Spotted knapweed favours soils that are dry, barren, gravelly, or sandy.
Sunlight
Full sun
Hardiness Zones
10 – 12
Table
