Apply Tordon any time the weed is actively growing. The Tordon label prohibits seeding perennial grasses the same year this herbicide is applied. Earlier applications do not control the weed effectively. Fall is a good time to apply Telar, but it may injure smooth brome or other brome species. Optimum timing for Escort is similar to Telar.
Russian knapweed tends to form monocultures and usually eliminates other plants.
Therefore, sowing desirable plant species is necessary after the weed is controlled. Smooth brome will compete with Russian knapweed. Research shows that streambank wheatgrass, thickspike wheatgrass, crested wheatgrass and Russian wildrye established after Russian knapweed was suppressed with herbicides. Sod-forming perennial grasses, like streambank or thickspike wheatgrasses, help prevent reinvasion better than bunch grasses like crested wheatgrass. 1 Colorado State University Cooperative Extension weed specialist and associate professor, bioagricultural sciences and pest management.