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Species
Information
- diffuse
(white) knapweed
- Centaurea
diffusa Lam.
- USDA
Symbol: CEDI3
- Oregon
Noxious Weed Designation: B
- Pictures
Identification:
Biennial; flowers midsummer to fall. Grows to 3 ft tall. Single-stemmed plant with numerous lateral branches. Flowers white to rose, sometimes purplish. Flower heads slender with pointed, fringed bracts. Spreads by seed, aided by the tumbling of windblown mature plants.
Impacts: Diffuse knapweed will form dense stands on any open ground, excluding more desirable forage species. On land where it is well established, the control measures are often more expensive than the income potential of the land. It is very drought tolerant, which allows it to grow under a wide range of conditions, including riparian areas, sandy river shores, gravel banks, rock outcrops, rangelands and roadsides.
Biological
Controls: There are 14 biocontrol agents approved for release, 13 of which are established in Oregon.
Oregon
Maps of Diffuse Knapweed Distribution
Links:
USDA
Plants Database information on diffuse knapweed
GRIN
Database information on diffuse
knapweed
Oregon Department
of Agriculture information on diffuse
knapweed
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