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Publications: Noxious Weeds
in Slow Motion: A
talk by Jerry Asher about noxious weeds in the Blue Mountains
Click on a weed to learn about how to find it and kill it!
- Stems: From 1 to 3 feet in height. Stiffly branching
with branches more or less erect and roughly ridged.
- Leaves: Divided feather-like into narrow segments (except
the uppermost). Leaves of the basal rosette are 6 inches long.
- Flowers: Solitary on each branch tip; purple or rarely
cream-colored; the outer flowers are enlarged. Flower heads are
1/2-inch wide. Flowering period is from June to September. Flower
head bracts have dark fringe at top resembling a spot.
- Seeds: About 1/8-inch long, tan to dark brown, and tipped
with plumes that fall off at maturity.
Spotted knapweed is a biennial or short-lived perennial that is
generally somewhat woolly. It infests roadsides, waste areas, and
rangelands; it seems to prefer more moisture than diffuse knapweed.
It spreads by seeds carried by wind, animals, or people; it can
produce 25,000 seeds that stay viable for 8 years.
***WARNING: All knapweeds
may contain a cancer-causing agent.***
***Handle with extreme
Control: Integrated management is necessary to control this
- Mechanical: Hand pulling small infestations, and reseeding
disturbed sites with desirable species. Wear gloves when pulling
- Chemical: Herbicide application can work. Consult you
local weed control office for more information.
- Biological: Twelve insect species are cleared for use
by the USDA to control spotted knapweed. Each insect attack reduces
the plant's overall seed production by weakening the plant or
eating the seeds.
Report all sightings to your local