Japanese Knotweed Polygonum cuspidatum / Fallopia japonica By Jerry Cunningham

What is an alien invasive species Recently introduced (last 200 years) Not a normal component of ecosystems Present due to careless or deliberate human introduction

How did it get here Introduced in the late nineteenth century Ornamental from Asia (Japan, China, Korea)

Description Upright, shrub-like, herbaceous perennial Membrane sheath above each joint Leave size may vary Greenish white flowers in summer Small winged fruits

Geological Distribution Through most of North America Particularly abundant in Eastern US and the coastal areas of Washington and Oregon Canada

Biology Variety of soil types – loam, sand, & PH from 4.5 to 7.4 Early spring shoots appear Rapid growth Flowering in late summer

Reproduction By vegetative means in US Dispersal is through distribution of root material Rhizomes in 1m 2 can produce 238 new shoots

Why is it a problem? Forms dense thicket that exclude native species Little value to wildlife Spreads through river systems and out competes native plants better suited to control erosion

Control Mechanical - repeated cutting reduces vigor Chemical – foliar spray of glyphosate (early June and again late August) Biological – no options currently