Plant has been covered by dark spots and looks like big bites
This looks to be Shot Hole Fungus. This will need to be treated with a fungicide. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
This article will give you information on the care of Hydrangea plants: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm
I have several Hydrangeas, lots of green leaves with little or no flowers. Some have a few flowers inside of the plant or underneath of the plant. I do not cut them down in the fall or spring. I live in North Olmsted, Ohio Zip 44070. Cold winters. Pictures attached.
It may have to do with the type of hydrangea and whether it blooms on old or new wood. If, for example, it blooms on old wood and died back during the winter, the new growth won't have buds.
Read more:
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm
The bushes are extremely healthy. They are pruned every year. Not given any plantfeed/fertiliser. What can be done to encourage flowers?
It depends on the type of hydrangea. Timing of pruning is critical in certain varieties. Often unsuspecting pruners cut off the buds forming for the next season. Here is more:
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/deadheading-a-hydrangea.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/mophead-hydrangea-care.htm
I would like to know when is the best time for me to cut down my hydrangeas in southeastern, NC?
It depends on the type of hydrangeas you have. These articles tell you how and when to prune:
https://www.gardeningknowhow.com/ornamental/shrubs/shgen/pruning-old-and-new-wood.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/deadheading-a-hydrangea.htm
The plant gets morning sun. We live in Newport Beach near the water.
This can have many causes from too much sun to too much water! This article will help you to care for hydrangeas: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm
The plant is quite large but hasn’t produced flowers in 2 years straight, and it’s really healthy.
It, more than likely, has everything to do with the type of hydrangea that you have, and your climate zone. If they die back to the ground every year, and don't flower, then they likely flower only on old wood. If there is no old wood, then there will be no flowers.
Other issues can include too much nitrogen, or not enough phosphorus and potassium in the soil.
This article will offer more information: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/hydrangea-not-blooming.htm
This article will offer information on the proper care of hydrangea plants: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/growing-hydrangeas-hydrangea-care-guide.htm
I have a hydrangea vanilla fraise in a pot. It has been such a magnificent specimen this year and I think it needs repotting. What size should I be looking to get?
When you pot up a plant you will want to use a container that is, only, one or two inches bigger on all sides. This will prevent overwatering issues, and give it some extra room to grow.
These articles will help: https://www.gardeningknowhow.com/houseplants/hpgen/repotting-a-large-plant.htm