"David Hill" wrote in message
...
"...Without doubt Persicaria....Also it can grow almost 2 inches in a
week
...."

Must have been having a brainstorm, or just hunger got to me, should read
12 inches a week... yes 1 foot.
If you have a few young ones then a couple of weeks of warm wet weather
you
will wonder where all the other plants have gone. They will have been
swamped.

I haven't found it to be quite such a pest, I've had it growing quietly in a
corner which I've simply hacked into periodically to keep it in check.
Certainly not something you'd want in a low maintenance garden, but not in
my opinion uncontrollable.