Height to 4 ft.; rosette first year. Spotted knapweed is a prolific seed producer, with individual plants producing up to 140,000 seeds per square metre. micranthos (Gugler) Hayek (Aster family, Asteraceae) Description . Invasive Plants in Pennsylvania: Black, Brown and Spotted Knapweed (PDF | 1.2 MB) Pennsylvania Department of Conservation and Natural Resources. Spotted Knapweed is one of 3 targeted plant species in Minnesota with an active bio-control program, the other 2 species are leafy spurge and purple loosestrife. Stem Description: Spotted knapweed stems are upright and branched, with larger plants being more branched than smaller plants. Seeds and plant fragments make their way into hay and the undercarriages of vehicles, allowing for new infestations over great distances. Spotted & Diffuse Knapweed. See also: Invasive Plant Fact Sheets for plant species (trees, shrubs, vines, herbs and aquatic plants) that have impacted the state's natural lands It is also an invasive species in the United States, and particularly widespread in dryer regions of the Pacific Northwest. NUTRIENT VALUE The rosettes and young flowers of spotted knapweed have some nutritive value. Seedlings Cotyledons round at the apex and narrowing to the base. Spotted & Diffuse Knapweed Centaurea biebersteinii, Centaurea diffusa. Spotted knapweed is primarily a weed of pastures, hayfields, roadsides, and sometimes turfgrass. Description. Description: Spotted Knapweed is a biennial or short-lived perennial with several branched, upright stems growing from a stout taproot and usually grows up to 3 feet tall. DESCRIPTION Spotted knapweed is a biennial or short-lived perennial. Spotted knapweed typically forms a basal rosette of leaves in its first year and flowers in subsequent years. ND-Spotted Knapweed (NDSU Extension) (CEBI2) NJ-Rutgers Cooperative Extension (CEBI2) OH-Ohio Perennial and Biennial Weed Guide (CESTM) PA-Pennsylvania Flora Abstract (CESTM) Plant Conservation Alliance-Alien Plant Working Group (CESTM) TNC-Global Invasive Species Initiative (CESTM) USDA FS Fire Effects Information System (FEIS) (CESTM) Centaurea stoebe, the spotted knapweed or panicled knapweed, is a species of Centaurea native to eastern Europe. Rosettes are formed the first year and appear in early spring as deeply lobed leaves radiating from a common Spotted Knapweed Centaurea stoebe L. ssp. Spotted Knapweed was formerly (or incorrectly) known as Centaurea biebersteinii and Centaurea maculosa. Report a Sighting. Weed Description A biennial or occasionally perennial that forms a basal rosette during the first year of growth and produces a flowering stem during the second year. State designated noxious weed. Spotted—pink to purple finely dissected compound daisy flowers with black fringe; June to September. A study by Kelsey and Mihalovich (1987) found that spotted knapweed collected before flowering contained neutral detergent fiber (24.2-53.0% in dry weight), ether extract (3.1-9.0%), crude protein (6.2-18.2%), total non-structural carbohydrates (11.0- 27.5%), ash (4.9 to 9.3%), in vitro dry … Its name is derived from the spots formed by black margins on the flower bract tips. Seeds have short bristles (pappus) on one end. Fruit/Seed Description: Seeds are 0.1 inch (2.5 mm) long, black or brown and oval.