[Fleeceflowers and Knotweeds: The Genera Aconogonon, Bistorta, Fagopyrum, Fallopia, Persicaria and Polygonum East of the Cascades of Oregon and Washington]
Common Knotweed, Doorweed, Prostrate Knotweed,
Yard Knotweed
Polygonum aviculare
Prostrate knotweed as seen along Forest Service Road #1647 in southeastern Logan Valley, Malheur National Forest........August 3, 2011.
- 
The photo above and below show close-ups of
the leaves and flowers of prostrate knotweed as seen along road #82 at Snowking
Snowpark on the southern slopes of Mt. Adams........October 2005. Note
that the outer and inner series of tepals in individual flowers are the same
length.
Paul Slichter