Limited distribution in Utah. High priority to eradicate all known populations and prevent new ones.
Quick Facts
Report your sighting through EDDMapS to help us track and respond to new infestations.
Report on EDDMapSJapanese Knotweed
Polygonum cuspidatum
Overview
Japanese knotweed is one of the world's most invasive plants. It forms dense thickets that exclude native vegetation and can damage infrastructure including roads, foundations, and flood control structures. It spreads primarily through vegetative fragments and is extremely difficult to eradicate.
How to Identify
Hollow, bamboo-like stems 6-15 feet tall with distinct nodes. Large, heart-shaped leaves with flat or slightly indented base. Small white flowers in late summer. Reddish-brown stems in winter. Spreads aggressively via rhizomes.
Control Methods
Repeated cutting can suppress but rarely eliminates. Herbicide treatment is most effective. Multiple years of treatment required. Never compost or move plant material - even small fragments can start new infestations.
Herbicide Recommendations
Glyphosate or imazapyr applied to cut stems or foliage in late summer. Triclopyr is also effective. Multiple treatments over several years required.
⚠️ Always read and follow pesticide label directions. Contact your county weed superintendent for site-specific recommendations. Permits may be required near water.
Need help managing this weed?
Skyline CWMA can connect you with technical assistance, cost-share programs, and licensed contractors for treatment on your property.
