"Brian" expounded:

Japanese Knotweed is a very variable plant. In Japan it is no more than a
decorative plant frequently used in their gardens.
Outside of Japan control will patently vary. A large clump locally has
been cut to ground level at monthly intervals for about fifteen years and
still persists though with less vigour than originally.
In my daughter's garden we cut the stems to about 12" and filled the
hollow stems with agricultural strength Roundup. It decreased annually and
was gone after four years.

It is everywhere around here, hubby and I were just taking a ride over
in Scituate and I pointed it out along the road in many places. Fill
dirt frequently has roots in it, and so it goes.

Four years? I'd rather be rid of it in two! G
--
Ann, Gardening in zone 6a
Just south of Boston, MA
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