The general answer is yes..Hakone grass can be divided. Unfortunately, this is the wrong time of year to do it. Division should be done in spring or fall, but never in summer. It's a cool season grass, and will probably be blooming soon, and the combination of blooming and summer weather really reduce the chance of the divisions surviving. Further...Hakone is only hardy to zone 5, and iffy there.

I've seen it growing in the Twin Cities and I have a friend growing it "in town" in my area. I have not been successful in growing it. I'm on the edge of the prairie and get a lot of wind. Even my most sheltered spots are windy. I'm not sure if it was the winter winds that did it in or if just didn't stay moist enough or a combination of the two. Either way I lost two of them and have pretty much given up on it for now. Good luck, whatever you decide.

You never want to overly disturb the roots of an established Japanese maple........it is just an invitation to disease. Hence the response above. Gently remove the grasses that are not thriving and relocate them elsewhere. Replace them with mulch or a very shallow rooted groundcover, like London Pride (Saxifraga x urbium).

I would trade for your Hakone. I have bergenia, several varieties of hosta,daylilies and hydrangea. Should I send some pics?