Posted: 07/04/2016 at 09:50
I wouldn't have planted a Hydrangea petiolaris in a container - they grow into big hungry plants and need lots of nutrition and water. If I did put one in a container it would have to be a very large one containing John Innes No 3 loam based compost.
If you've used an ericaceous peat based or multi-purpose compost it's unlikely to be happy there for long. It is also the preferred home of vine-weevil grubs which will eat the roots of many plants.
When you take it out look for vine weevil grubs among the roots