Synonyms:
- Centaurea biebersteinii, C. maculosa, Acosta maculosa
The Plant:
- A biennial or short-lived perennial, 1-3 feet tall, with a stout taproot. Slightly pubescent, with one or more branched upright stems.
The Leaves:
- basal
- up to 6 inches long
- blades narrowly elliptic to oblanceolate
- entire to pinnately parted
- stem leaves pinnately divided
The Stem:
- multi-branched
- thin
- wiry
- coarse
The Flowers:
- Thistle-like flowering heads with many petals. The ray flowers are pinkish purple, seldom cream colored. The involucral bracts are stiff and tipped with a dark, comb-like fringe. Blooms from June to October.
The Fruits:
- brown and dry, 1/8 inch long
- tipped with a tuft of persistent bristles
The Habitat:
- dry, gravelly sites
- waste places, disturbed soils, roadsides
Dispersal:
- stick to animals and humans
- wind
- contaminated hay
- can resprout from lateral root buds or from crown of leaves, especially following attempts at removal
Key ID Features:
- thistle-like, pinkish-purple flowers
- stiff bracts
- fruit topped with bristles
- wispy foliage
Similar Species:
- Russian knapweed (Centaurea repens), Cornflower (C. cyanus), Diffuse knapweed (C. diffusa), Black knapweed (C. nigra), and Brown knapweed (C. jacea) all have similar inflorescences
- Other knapweeds lack the black-tipped flower bracts that are characteristic of this species.
Notes:
- Spotted knapweed can invade and seriously effect the biodiversity of an area, by choking out native vegetation. Erosion occurs due to its inability to hold the soil. Hand-pulling, cutting or mowing over several years may successfully eliminate Spotted Knapweed. ; On Nantucket, this species has been seen growing along the Madaket bike path heading west
Growth Form: Herb
Origin: Europe
Level of Invasiveness for Nantucket: Invasive
Level of Invasiveness for Massachusetts: Likely Invasive
Massachusetts Cultivation Restrictions: importation ban, propagation ban
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