In article ,
says...

Looks like one of the knotgrasses (Polygonum sensu strictu). I won't
take a guess at the species; quite possibly you've got a different set
of possibilities compare to my location.

Oh, yes, location -- central Puget Sound, between Seattle and Tacoma.

--
is Joshua Putnam
http://www.phred.org/~josh/
Braze your own bicycle frames. See
http://www.phred.org/~josh/build/build.html