Abstract:
Knapweeds are a serious problem in Oregon because they vigorously
invade disturbed or degraded sites and form dense populations that exclude native and desirable plant communities, causing economic and
ecological losses. Their ability to spread rapidly by seeds and
roots makes control very difficult. Seeds can remain viable for 5 years or more, and once a large number of seeds builds up in the soil,
it can take years to eradicate knapweeds from that site.
