While watering this morning (with this thread on my mind) I found one of our older Dendrobiums against the greenhouse wall, one of whose canes had multiple spikes which had been cut off about an inch from the PB. The base of one of those spikes had a keiki growing from it, which itself had bloomed and whose spike was now brown and dry. So apparently, some Dendrobiums (this one's a NOID Dendrobium Phal) *will* keiki from an old flower spike. This is the first time I've ever seen that, and I'll take a pic as soon as the cam's batteries are recharged.