land, I'm trying to picture what you did in Fall...

You say pruned off all the branches that were dead - were you cutting into truly dead wood then, or just leafless branches....I would have expected new growth to begin to sprout from somewhere below but near your cuts, not just from the very base.

Growth buds on rhododendrons form in the leaf axils - where leaf joins stem, or where there once were leaves if too much shade has caused stems to become bare. When you have to cut into a branch without leaves or far below any existing leaves, often you can see faint rings in the bark that mark where leaves once were...the dormant buds are just below those rings - you may even be able to see small bumps. Leaving some of the framework is going to leave more dormant buds, as opposed to cutting clear to the base.

If you can't find the rings, you may go ahead and cut where you must, then go back later and remove any bare stubs above new growth once they've sprouted.

You've already figured out that Fall isn't a great time to do restorative pruning, it doesn't give new growth time to mature and harden before winter weather.

Spring would be a better time, and if the root systems are healthy, shade/low light being the reason your rhododendrons weren't thriving, hopefully they will respond well to pruning and better conditions. Two schools of thought on the fertilizer - these shrubs have low nutritional requirements and usually less (or none) is better than more; but, a one time application can also kick start growth on a rhododendron that is reluctant to sprout on very old wood, so the age of your plants comes in to play here.

Thanks for responding, Morz. The plants had some branches with leaves, some branches with no leaves, and some branches that were clearly dead. By clearly dead I mean that they were gray and brittle. Those are the ones I pruned off. I left quite a bit of wood that appeared to still be alive, but had no leaves.

The sprouts actually popped up from the base of the plant where all the other branches were coming up from the ground. I don't know if that is good or bad.

The plants now are about six feet tall and mostly bare. I guess my question is, would pruning them back in the early spring encourage new growth, or should I just leave them alone and see what happens now that they are getting light again?

A little of both? :)

I think by the time the daylight hours lengthen and it's warmed up a little, you may know if any growth is going to happen naturally....careful examination should reveal slightly enlarging little nodes/bumps along the stems.

They would probably benefit from pruning back the legginess they've taken on while deprived of light if you want these to be a focal point of your entrance any time soon. Mulching the root zone well and paying attention to water again next year will help them too....

I wouldn't touch them until this spring when you see what you have. Hopefully more shoots will come up. If and when new growth starts coming, you can start pruning back for shape. The conservative rule of thumb is to never remove more than 1/3 of the leaves in any year. You want to force this plant to generate new growth. Pruning will do that, but it is in a weakened state from the vine, so don't over prune. When it starts looking better, you can apply some Hollytone in the spring, but I wouldn't force it this year. It is too fragile now.

Here is a link that might be useful: How to grow rhododendrons and azaleas.