Stevens County Noxious Weed Control Board
This web site will help you identify & control noxious weed with information and photographs to aid you.

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Bighead knapweed
Centaurea macrocephala Puschk.            
Sunflower family

Key identifying traits

  • Single, 1-3" wide, yellow flower heads on erect, unbranched, leafy stems 2-5' tall
  • Broadly lance-shaped leaves have sharp pointed tips, shallowly toothed edges and rough surfaces
  • Leaves change from simple stalks to winged stalks to no stalk as they become smaller up the stem
  • Bracts surrounding the flower head are wider than long, mostly brown with lighter margins appearing in 8-12 layered rows
  • Seeds are " long with pale to brown plumes

Biology and ecology

  • A perennial that reproduces by seed with up to 200 seeds per head
  • Sold commercially as an ornamental under the names "Lemon fluff" or "Globe centaury"
  • Found only as an escaped ornamental to date but competes vigorously in heavy grass stands in areas with loam soils and 20 inches of precipitation
  • Remains green in August & palatable to livestock
  • Generally has only one or two stems 2-3' tall with 1"  heads when found competing with grass but as an ornamental may be 5' tall with 3" heads on each of multiple stems

Control

Prevention Learn to identify plants; know your property; beware of aggressive ornamentals

Biological None known

Cultural Competing vegetation helps limit spread

Mechanical Repeated tillage, digging or cutting are all effective if properly timed to prevent seeds

Chemical Several can be effective if applied early in growth cycle;  refer to the PNW Weed Management Handbook for specific chemical recommendations

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Where found
Only occasionally reported as an intentionally planted ornamental in Stevens County but is in known as an aggressive escaped ornamental in northern Pend Oreille County and in Whitman and Okanogan Counties in Washington.

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weedboard@co.stevens.wa.us
Last Edit: March 25, 2015
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