Japanese Knotweed, Polygonum cuspidatum, is a very invasive perennial.

I have a smaller growing type of knotweed that I bought about 15 years ago. It looked beautiful with its pink tuft of flowers. Little did I know what I was in for. Every year I think it is all gone, but more seems to pop up. I can't do anything too drastically, because it is growing next to my fish pool. Everyone seems to like it except me. I should have known better, since I am a master gardener.
Bill

I'm suprised no one has posted a bit more emphatically about this plant. It is on the noxious weed list of nearly every state in the nation as well as many foreign countries. It is extremely adaptable to a variety of conditions and has naturalized rampantly in some ares. In my state, erradication, if growing on your property, is a requirement.

There are supposedly non-invasive cultivars of Polygonum cuspidatum, but I wouldn't like to test that theory:-) Most members of this family - that includes persicaria, fallopia, tobira as well as polygonum - have very aggressive growth habits, although few that I know of that are quite so incredibly rampant and robust as the Japanese knotweed.

Your reference to the bamboo forum is not all that unusual - another common name for this plant is Mexican bamboo. The hollow, jointed canes do resemble those of bamboo and many bamboos can spread just as aggressively as the knotweed. And they are not any harder to remove from unwanted locatons :-)

In short, get rid of this plant or encourage your mother or her friend to do so. It's a menace!

Here is a link that might be useful: Japanese knotweed

Wow...thanks for your posts...I am totally shocked! The knott Weed that my mother had was back in a corner of her yard...which is where I was going ot put some. It didn't seem to be out of control but maybe I just didn't notice. I have an area that is full of weeds and dumped dirt from where they dug my ponds (in the back of my dog run). Four yards join at this point and wanted something that would screen them off and maybe do away with the weeds.

My brother has some that has been in the same area for years now..he just mows right up to it mowing down new growth, I suppose.

I'm wondering if maybe this is a more tame variety...if there is such a thing .:)

Thanks again for your input..
PJ

I have a clump forming type--I can't remember if it was sold as a Persicaria or a Fallopia but its cultivar name is Crimson Beauty. It definitely does not run, though it gets very tall, outstripping early in the season an immensely tall Eupatorium. Crimson Beauty blooms open white and turn red. It is a Japanese Beetle magnet, but it isn't invasive.

I am familiar with Japanese Knotweed which is invasive to the point of taking over the world. It is pretty much ineradicable.