Now is not an ideal time to prune. Colder weather later in the season could very well damage wood exposed by this late pruning and increase winter dieback. I'd wait until late winter/early spring after the worst weather has passed and examine for truly deadwood then and remove. Nikko Blue behaves rather idiosyncratically compared to most macs and will often produce blooms despite rather severe pruning. Regular fertilizing, as is necessary for any containerized plants, may encourage more flowers.

As to the look of the plant from the photos, if these were taken any time recently, I am confused as to what you are worrying about. It looks great, all things considered. It is the first of November afterall and even here in the rather mild PNW, most hydrangeas are looking pretty crappy - even more so now that we have just experienced our first hard frost. The only ones that look the slightest bit decent are the oakleafs which are in full fall color and hold their leaves well in cold.

Thanks Gardengal. The photoes are probably from a month ago, but as mentioned, the plant looks even worse now. The leaves almost have a faded, goldish tinge to them. They've never looked like this in Winters past, so I'm sure it's all due to that one time I didn't water, and the plant never really recovered.

I forgot to mention that even though the plant looks "bad", I have been seeing new buds coming up from the soil and the very bottoms of the stems. So I guess that means the plant isn't "dead" right? I was just so afraid that the plant was on its way to actually "dying", it just looks so bad compared to usual.

OK, so maybe around the end of March, I'll see if I should do any pruning.

Tx!

I'm surprised they are showing any foliage at all at this time of year in your zone and the pale yellow, faded look is not all at odds with the season. If showing buds, the plant is fine and healthy. Keep well-hydrated through winter and in a protected location where the container is not subject to freezing. Prune as necessary later.

You do know this plant is not evergreen and it will lose all its foliage over winter?

Thanks Gardengal. Yes, I do know that it will lose its foliage. I was just concerned because the leaves had faded and curled, well before they should have, and almost immediately after I'd neglected to water it for about a week's time. So I feared I'd somehow "killed" the plant, since from that point on, the appearance of the plant never improved, and it still the end of Summer.

Anyway, I'll just protect it as normal for the Winter.

Tx.