"can the blooms be saved by covering the hydrangeas for the winter?" Depending on location, may not be just as simple as 'covering' the hydrangea. Successful winter protection generally involves a bit more then mere covering :-) There have been many, many discussions on this forum over the years on methods of winter protection and here is a link that will connect you to many of them: https://www.gardenweb.com/discussions/hydra/query/winter-protection/nqrw I can't tell you which works best, as there is no need for this in my climate. But I do suggest winter protection for anyone living in zone 6 or below but zone 7's may benefit as well, as it is often the wide fluctuations in spring temperatures that cause the most bud damage. I'd also recommend this for new wood bloomers as well, as the less dieback from cold weather involved, the more vigorous the new growth will be and the greater the chances for flowering. This protection only involves Hydrangea macrophylla cultivars (and closely related serratas), as the other commonly grown species are more cold tolerant and bloom reliably on new growth.

My mother has a plant that came labeled as Nikko Blue. However it dies back to the ground every year. So I cut off all the old stalks in spring, clean up the clump and let the new growth come on. One year I left old stalks, but they got no new growth, just dried out old stems. Blooming on new growth each year, there really is no shaping to be done. No old woody stems either. Gets about 40 inches tall, nice and lush, fuller over time. So I have to wonder if plant was mislabeled or if it grows differently in other locales. She is solid z5, with cold winters, deep snow, just south of Kalamzoo. Plant comes back nicely each year, blooms well, mid-july. Lovely flowers, very full, last a long time.

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.

Mopheads like NB develop flower buds on old wood, between July and August (around July for me and August for you). The buds can withstand winters up to Zone 6 but only if the plant goes dormant without problem in the Fall, if the winter temps are not too cold for your zone, if the plant continues to get moisture before the ground freezes, and if the plant does not break dormancy due to high temps in winter. if you want to get reliable blooms from those buds, you need to winter protect. You also need to protect in cases where the weather stays warm but temperatures suddenly come crashing down (like 25 or less). High temps can make the lants break dormancy. Then sudden and large drop below 32F can kill the buds. Down here in Zone 8, mopheads, lacecaps and oakleafs are alive, green and well as if this was September. Paniculatas went dormant a few weeks ago. So, I am concerned about damage from a sudden large drop in temps under these conditions. Two winters ago, winter started late, the plants did not go dormant in the Fall and December had a nasty temp drop from the 70s to the 20s that continued for a while. Last year, the same thing occurred but in the 1st quarter of 2015. Both scenarios killed flower buds. So this year, I am trying to winter protect the hydrangeas like NB that bloom on old wood. You might winter protect if you want to make sure you get bloomage in Spring. Since my leaves are still a nice, lush, green or red, I just put the chicken wire around the plants and will add mulch either before there is a large drop in temps or after gradual/small drop in temperatures dry out the leaves. By the way, which Ilex do you have? I was looking at one deciduous holly that produces yellow 'berries' (drupes) because I have several fruit producing shrubs around but no yellow 'berries'.