Key identifying traits
- Flowers are pink to
purplish-red with light to dark brown fringed bracts that can
give a golden sheen appearance to infestations
- Flower heads are larger
than either spotted or diffuse knapweed
- Grows up to 3 ½’ tall
with many branches
- Leaves may be
entire, coarsely lobed, or toothed but not divided as in diffuse
or spotted knapweed
Biology and ecology
- A perennial plant
spreading by seeds
- A fertile hybrid between
brown and black knapweed
- It is a native of Europe
- This plant is found in
throughout the Pacific northwest; denser populations in western
WA but some sites known in Pend Oreille County
- It invades fields and
pastures as well as roadsides, open forests, and moist areas
Control
Prevention –
Learn to identify plants; start monitoring early in the season
Biological –
Larinus minutus is effective and widespread in our county
Cultural –
Plant competitive cover crop
Mechanical –
Does not tolerate tillage but may need to be done more than once;
grazing or mowing not effective unless it is done continuously,
small areas can be pulled or dug
 Chemical
– There are many products on the market listed for control of knapweeds
such as; 2,4-D, dicamba, glyphosate: refer to the
PNW Weed Management handbook for specific chemical
recommendations
|
Cindy Roche, www.forestryimages.org |
