Am I too late this Spring (April 26th) to attempt to divide and transplant from established grove of black bamboo culms.
No. Even if sprouting and new sprouts are lost transplants will not die as long there is enough rootstock with buds for additional sprouts. In fact, you can move and replant individual culms with a tuft of roots but no buds and have those live until they reach the end of their natural span. This method is used to produce 'groves' that do not spread and have to be curbed - at least until they have to be replaced.
