Hope someone else has tried and chimes in. They (cuttings) are not common here in Texas so I have not tried. Dr. Dirr said it was very difficult (he had "miserable success") to root; that cuttings should be collected while the shoots are still pliable, soft and green but that somehow, wholesalers manage to do better than he. You can also sow the seeds on the medium's surface and keep them moist.

I only tried once and failed. You may find useful info in this old post…

https://www.gardenweb.com/discussions/1992098/propagating-climbing-hydrangea#n=16

tj