I have seen very well behaved varieties and of course there are the incredibly invasive varieties.

These pictures look a lot like the variety I had. I planted 4 of these from 3" pots about 3 years ago. I needed to remove them this year for an irrigation system. After 4 weeks of repeated applications of glyphosate, I ended up having to dig them out of the ground. The roots were 2-3 feet deep. It's an incredibly tough plant. More like a very hardy shrub that grows anew each year than a typical perrenial.

It was a pretty plant when they were young then they were a huge nuissance. I was constantly pruning to keep them under control. I would not recommend them unless you want them to take over a fairly large portion of your yard.

Aaron

Here is a link that might be useful:

I may be off-base but I think Japanese knotweed is invasive by virtue of its ability to be seeded by birds far and wide, thereby pushing out natives and more well-behaved plants far from the site of its original planting. Please do your community and neighbors a favor and avoid this marauder. (I wish my neighbors would!)

You can come and dig mine up I want it gone it is very invasive no matter what kind!!

Carol
Mishawaka,In