Anyone try this, I have a huge patch growing by a small creek at work? Mike

No, no!

Care to go a little more in to the explanation?
Thanks,

It looks like bamboo, thought it might work?

Jap knotweed doesn't have the structural strength to make a useable arrow. Generally its diameter is too large, walls too thin and center void too large to make a useable arrow.
  Knotweed has a segmented stem like bamboo but there is nothing else I know of that makes it look like bamboo.
  There are lots of materials that are proven to make good arrows from many species of boo or cane, many hardwood and softwood shoots and even some weeds like horseweed and goldenrod.
 The way I determine if a plant will work as an arrow is to collect a bundle of shoots that are a little bigger in diameter than an arrow(allowing for shrinkage), bundle them up with rubber bands or cordage, store in a dry location and give them a month to dry. Then see how they hold up to flexing and recovery and if they can be straightened and hold their shape.
 I have never tried knotweed but from trying to eliminate it(I do landscape work) I know it's top growth is not structurally sound as far as using it for arrows...at least not for me.

Thanks Pat!

Thanks Pat!

ok thanls , I had nothin to compare it too,  Mike