Knotweed

(a.k.a. Japanese Knotweed, Giant Knotweed, Mexican or Japanese bamboo, fleeceflower)  

Gravel Bar Growth

 Distinguishing Features  

• Thick green to reddish stems that look similar to bamboo
• Large bright green leaves ranging from egg to heart-shaped with a pointed tip
• Sprouts in April, grows to 15 feet tall or more by July
• Spikes of white flowers appear from July to September
• Seen in flood zones along rivers and creeks, also frequents ditches and yards

Photo by Britt Slattery, USFWS

CAUTION–DO NOT MOW

Knotweed is considered extremely invasive. Tiny root fragments can produce new plants and often travel by waterways. 

To date, knotweed has been treated along 27+ miles of the Calapooia River, and infestations in the lower watershed were inventoried and treated during summer 2009.   

Knotweed Foliage

Resources on Japanese Knotweed   

• The Oregon Department of Agriculture’s page on Japanese knotweed 
• The Oregon Department of Agriculture’s page on Himalayan knotweed
• Oregon State University Extension Service’s Knotweed fact sheet
• Knotweed fact sheet by the Plant Conservation Alliance
• TNC Knotweed Brochure