Dig out the entire root system, including all rhizomes
Remove and bag all plant material for disposal
Repeatedly cut or mow new growth throughout the season
Apply a systemic herbicide to actively growing plants, following label instructions
Re-treat regrowth until no new shoots appear
Cover the area with a heavy-duty root barrier or impermeable membrane
Monitor the site regularly for several years
Dispose of contaminated soil and plant waste according to local regulations
Hire a licensed invasive-species removal professional for large infestations
Prevent spread by cleaning tools, boots, and equipment after use