thanks for the feedback. i happened to be at bamboo headquarters
yesterday and described my unknown bamboo, and they were quite certain
it is a bambusa vulgaris 'vittata'.

http://www.bambooheadquarters.com/photoweb/bavv.htm

apparently the relevant bits to them were a) size of grown plant, b)
basic coloring, c) culm ( grooved or not ), d) growing location, e)
propagation method. since it was propagated via culm cutting this gave
them the "ah ha" they were looking for. i was relieved.

picked up a couple of nice pleioblastus while i was there... =)