Ian:
    Japanese knotweed or Mexican Bamboo (Polygonum cuspidatum) honey is
usually mixed with aster here but is light and mild.  It is in the Buckwheat
family, but one of the mildest of this group, which includes smartweed.  It
thrives in wetter areas, such as drainage ditches and along brooks and
rivers, where it is an excellent erosion control.  It has no thorns and is
edible, I've heard.  It's origin is Japan.  It reaches 8 feet in height.  It
is still in full bloom here in southwest NH and southeast VT.
Charles Andros