Plant ID

[Enigma]

I ran across this Tuesday walking some new ground. First time I saw it I was 50' above it looking down a steep hillside. Looked odd. Too green for December in CNY. Found myself at the bottom of the same hill later in the day. There was a 1/4 acre of it easily. At first I thought it was bamboo. A friend of mine had some at his place but that stuff was huge. This was small. And green stem. 

I'd forgotten what it was but one text to the same friend and he nailed it. +1 if you can identify it sans google. Prehistoric stuff.

[G-Man]

Horsetail.