| First off, I titled this post with the common name and not the botanic because there seems to be a huge disagreement as to the correct botanic name. Anyway, I have a different question than the taxonomy of this plant and don't want to sidetrack the discussion.
I have been growing the variegated version of this plant, which is most commonly sold as Fallopia japonica 'Variegata', for about seven or eight years now. The plant spreads a bit by underground runners but has been very easy to control. I have had no concerns about this plant being invasive.
Early last winter I was walking in the field about 1000' behind my house and garden and came upon the remains of a stand of plants that I did not recognize. Of course, at that point there were no flowers or leaves to speak of to aid in identification. The stems were at least five to six feet tall and reminded me of bamboo.
Flash forward to August when everything is green and growing, and I realize that I have a stand of Japanese knotweed on my hands. Now this location is not next to flowing water, and it is a fairly isolated spot well away from anyone else's gardens, as in it is at least one mile or more to any cultivated garden other than my own.
My concern is where these plants could have come from, and more specifically, could seed from my 'Variegata' plants have created this colony? These plants truly appear to be the straight species and show no evidence of the variegated form. Besides the leaf variegation, the 'Variegata' gets only about four feet tall and very branching, while these plants are much taller and very upright.
Anyone have any insight on this?
V. | 
