There are a number of things it could be, and without a picture I can't be sure of its identity. However, with a few questions we can narrow it down.

Does it have yellow stripes down the culms?

Does it look like this?
{{gwi:401840}}

if so its Phyllostachys aureosulcata. Otherwise it is probably still a Phyllostachys. Take a look at http://bambooweb.info/Plants.php and scroll down to the Phyllostachys section and start looking at the photos. Good luck with your divisions. I'd keep them indoors until Spring arrives.

I agree with Brian. Most likely its the common bamboo out east, yellow groove, Phyllostachys aureosulcata. Look for a yellow sulcus to be sure.

It is probably yellow groove bamboo.

Lately I have done much work in talking to plan growers and such.

Most of this type of bamboo can be found growing around the
Allentown area.

Yellow Groove is the heartiest types that can grow in PA.

It will loose it's leaves but it will grow and take over an area if you let it.

I know many areas where this type grows.
It is the most common.

I hope this helped you.