hello

While clearing some land in japan i have come across a grass with a bright red pith (if this is the right term for the center of the stem). It grows in clumps up to about a meter high and has a green blade with a central white line. the plant is green from the out side upon cutting it revels bright red pith.

I have shown this to a Japanese friend who is into native Japanese plants and he can not identify it. He has taken a cutting to see if one of his fellow enthusiasts can identify it.

any suggestions of what it might be?

thanks.