Confused about pseudo bulbs.
 

I have a question about pseudo bulbs. If a spike has been produced and bloomed off a pseudo bulb will that pseudo bulb ever produce a spike/blooms again? And if you have, say an oncidium with several old pseudo bulbs when you go to repot should you separate and toss the old and shriveled pseudo bulbs. In other words do old or back bulbs have any useful function after they have produced flowers. Always been confused about this and afraid to ask.
Pokey.

As long as old pseudobulbs are green, even if they are getting shriveled and have no leaves, they add strength to the plant. If the plant is big and healthy it doesn't really hurt to remove the oldest ones when you repot but you don't have to. Get rid of them if they are clearly dead though as they are just an invitation to rot at that point. Never leave a plant with less than 2 mature growths and a new growth coming if you can avoid it.

After a pseudobulb has bloomed it usually will not get another spike. There are some exceptions though - another reason not to remove a healthy one. A few orchids will rebloom from an old spike too.

PaphMadMan- thanks. Nice explanation and consistent with what little bit I thought I knew about pseudobulbs.

Yes, some orchids (take dendrobium bracteosum for instance) only bloom on old leafless canes and they bloom for years from the same canes.
I have a D. tanii that had only 3 clusters last year, and it will have 10 this year. Not only are the PBs that bloomed last year coming back in, but bulbs that are even older and some newer are also joining the show. Even some that appeared to be totally dead and rotted (lol).

Another useful function of old pseudobulbs is the propagation of new plants from them.

Subrosa. Please elaborate.

Mature pseudobulbs can be removed at repotting time and potted up separately. They will often start new growths.

I would caution you to not just throw away or even divide without a good reason (absolutely certain dead and/or won't fit in pot you're willing to put them in)...because increased size of the clump usually results in much better flowering...than dividing into many small plants.

Psuedobulbs that have already bloomed usually will not bloom again. However, they still act as a glucose and water storage vessel, allowing the plant to store tons of energy and water for blooming. Removing old psuedobulbs will weaken the plant overall - we do not recommend this.

If you do remove an old Psuedobulb, don't throw it away. Pot it up, keep it moist and it may produce a new plant.