I dug this one today with a friend. We were unable to get any mature culms, but we got some good sized root mass with some new shoots coming up. I'm not sure what the distinguishing characteristics of B. oldhamii are, but this one looks different from B. Vulgaris. Unfornately I didn't have my camera to take any pictures of the entire plant.
That's a 4" diameter B. vulgaris in the background.
Tristan