In message , Jake
writes
OTOH, if the OP forgets any thought of growing the japanese stuff, he
could investigate polygonum (or is it persicaria?) which is a legal
knotweed relative, such as p. campanulatum which is non-invasive. Many
of the relatives are, though, equally thuggish unless well contained.

Assuming that Fallopia sachalinensis (giant knotweed) should be eschewed
as being as bad as Fallopia japonica, the closest substitute might be
Persicaria wallichii. But I have the impression that this is rather
thuggish.

http://www.japaneseknotweed.co.uk/himalyan.php
--
Stewart Robert Hinsley