I really don't know but I do know that most hydrangeas like lots of water and I mean lots that's how it got its name hydo being Latin for water, so maybe being in a pot it needs more water. I may be wrong but worth a go 😊
Hi Frances hydrangea semannii is not particularly hardy so frost damage may be the cause, and if it is getting a bit too wet it may be suffering from a magnesium deficiency which often causes browning at the tip. What potting medium did you use for it if u don't mind me asking ?
Thankyou @carolgs @angiecrazycatlady and @icedance for your help . It's actually my daughters plant that was a Christmas present and she hadn't planted it so it has been in its original pot since then ! And I think kept inside for a period of time ! So as a temporary measure I just repotted it in that large pot in a multi purpose compost with some hydrangea feed & put feet under pot for drainage ! To revive it until she decides where it's to be planted properly .
Yes sounds like frost damage Frances if it had been inside then put into a larger pot and put outside it will have had a bit of a shock, it will come back once it gets into the ground but I would pop some fleece over if it gets very cold again and test the compost to see if it's wet before watering, like I say it should rally. they are notorious for not looking fabulous during the winter ❄️