A foot away is NOTHING for non-clumping spreading bamboos. Actually, Pseudosasa japonica is relatively well behaved. I have not found it to be anywhere as aggressive as aureus or a number of other species. I am in a zone 7 (with long hot summers) and have learned my lesson with other species. Lucky you planted japonica and not some really aggressive species.

thanks njoasis, i was just wondering because it was the only runner i planted. the other three are fargesia rufa,scabrida, and robusta and they are clumpers.

Be happy it lived... I like boo too much to be scared of it!