There are several different varieties of Ribbon Grass. Some are very invasive, and others aren't. In any case, in your zone, you should be able to control it pretty easily.

Don't over-water it. Use physical barriers to control it's spread. Root prune it to maintain the size you want. Shovel prune it to keep it out of places you don't want it to go.

Finally, there are lots and lots of grasses which are just as easy to grow, just as attractive and not at all invasive. Don't limit yourself to one type of grass. There are so many other forms, textures and colors to play with in the grass world.

Mine is in full sun and I rarely water it...kinda neglected, I guess is what I'm trying to say. LOL
Anyway, it stays put. I haven't had any problems with it becoming invasive as long as I'm not too nice to it. *grin

RENEE

I planted one ribbon grass last spring. I was kinda worried about having to control it too, but, find it hasn't "gone wild"-----yet. Mine is planted in full sun, and, a spot that doesn't stay "wet" too long. I am still working on that area and plan to have a rather thick mulch on it in a couple of weeks. That will help control it, too.