button,
The old canes are not dead, just lost their leaves. That knob might be a flower spike in the making. If you read Kevin's and Jerry's posts from
Nobile Dendrobium Himezakura thread, you'll see that nobiles produce flowers on the old cane which just lost its leaves.
Plus, looking at your pics, the canes are still green and firm. As long as they're that way, they're not dead.
