http://www.bhg.com/advice/gardening/vines/climbing-hydrangea-does-not-flower/

http://www.bhg.com/advice/gardening/vines/how-can-i-get-my-climbing-hydrangea-to-bloom/

Thank you kidhorn for your links. So, it appears that I just need even more patience and not to fertilize. The plant is now probably 70 feet tall, we have never pruned it (I don't think we could now if we wanted to!) My 16 year old son and I have been watching this plant for 10 years. He would get so excited over each years growth (just as he was growing,LOL).

They tend to be persnickety about blooming. Sometimes they have sparse bloomage until they hit the top of that which they are climbing. Then they go gangbusters.

I would fertilize the area around it since it has been 10 years with no fertilizers. Add a 1/2" to 1" layer of compost in Spring. Or sprinkle some cottonseed meal. And add mulch too if needed. A single fertilizer application in Spring will last all year since they are not glutons like roses. Add liquid seaweed, liquid fish and/or coffee grounds during the growing season to supply trace elements but stop all fertilizing in early July-August so it will go dormant on schedule.

The root system is extensive on these shrubs so apply the fertilizer past the drip zone. You may also want to do a soil test to confirm that nothing else is going on. Check the levels of Nitrogen, Phosphorus, Potassium and trace/secondary elements. But waiting until it reaches the top is common.

Luis

Blooming will be dependent on the amount of sunlight it receives - while climbing hydrangeas are very shade tolerant, they DO need sun to bloom well. Is it possible that the foliage on the oak when in full leaf obscures and shades a lot of the vine? 70' is a nicely mature vine and it should have bloomed by now provided it receives enough light.

Another consideration is that the vine may be receiving more fertilizer than it needs. If the oak tree it is climbing is in the middle of a lawn area and you fertilize your lawn with any regularity, the vine may be receiving excessive amounts of nitrogen, which will discourage flowering.