Thank you for an interesting question, but before I can provide any ideas I need a little more information.

   Has the plant bloomed previously?
 How old is the plant and have you done any pruning on it?

   If you could give me this information I may be able to provide some helpful suggestions.

 Thank you.

Hello-

Your Hydrangea symptoms are indeed odd.
I have a few additional questions before I make a response on possibilities.

Do you do any type of fertilization?

Do you know the variety of the parent plant that you got the cutting from?

Does the plant you got the cutting from have a similar problem or does it bloom ok?

Where is it located? Sunny or shady?

With these answers and the previous ones I should be able to give you some ideas and I will contact one of our members that grows a multitude of Hydrangea and get her opinion.

Thanks again and I apologize for the long assessment but as I said your symptoms are quite odd.

Again thank you for your question and additional information.

Based on your responses and research with other Hydrangea

gardeners we have a couple of suggestions you might consider.

Keep the soil moist but not to the point that it is soggy.

Hydrangeas love water.

 Apply a fertilizer that is recommended for Hydrangeas to

decrease soil pH to make it more acidic. This is to allow the

plant access to more soil nutrients. Also look for a fertilizer

that has a high Phosphorus (P) content. Look for a a fertilizer

that has a high P in the NPK rating or Bone Meal. Work

whatever you use into the soil and water generously. FOLLOW

the DIRECTIONS so as not to shock the plant! Another note on

selecting your fertilizer is try to keep the Nitrogen content (N)

lower. Nitrogen is needed but too much has a tendency to

decrease blooming while promoting growth. You may want to

consider having a soil test in the area of your Hydrangea to

determine the soils composition and pH.

 One of our members also suggested you may want to try

pruning it back in the fall to see if that promotes blooming next

year. I'm not sure I would recommend that unless you are

familiar with proper pruning of Hydrangeas as some varieties

are pruned at different times of the year and at different

locations on the stem.

  I have listed below several links that may be of help to you,

also listed is your County OSU Extension Service should you

want to reach out to them for advise.

 If we can be of further help do not hesitate to contact us. I

hope this will be of some help to you.

  Thank you again for allowing us to help you with your

gardening questions. Here are some other helpful websites

that may be of interest to you:

BYGL Newsletter: http://bygl.osu.edu/

OSUE Fact Sheets: http://ohioline.osu.edu

State Master Gardener Volunteer website - http://mastergardener.osu.edu

Ask-An-Expert website - https://extension.osu.edu/ask-an-expert

Ask-A-Master Gardener website -
https://extension.osu.edu/https%3A/extension.osu.edu/ask-an-expert/ask-master-gardener-volunteer

Montgomery County OSU Extension Office

580 Calumet Lane
Dayton, OH 45417

Phone:<personal data hidden>

https://www.tasteofhome.com/article/hydrangeas-not-blooming/

https://www.gardenerreport.com/hydrangea-not-blooming-6-solutions/

https://hydrangea.com/blogs/growing-tips/5-reasons-your-hydrangea-isnt-blooming

https://extension.oregonstate.edu/gardening/flowers-shrubs-trees/general-care-hydrangea

https://ohioline.osu.edu/factsheet/hyg-1263

https://www.thespruce.com/annabelle-hydrangea-care-guide-7507139

https://www.gardenfine.com/how-to-fertilize-annabelle-hydrangea/

https://www.bloomingbackyard.com/fertilize-hydrangeas/

Thank you so much for your time.  

   Your more than welcome.

If you remember let me know how this works out next year. This is something new to me also. I'v learned quite a bit from it.

Thanks again.