I have managed to strike several hydrangea cuttings over the summer.
M question is twofold.
!/ Should Iet them flower in the year ?
2/ I want to turn some of the ' Pink' ones into Blue ones. At what stage do I add Aluminium Sulphate ??
That should read 'Should I let them flower in the FIRST YEAR.
Personally I wouldn't. I'd let them develop into larger plants. I always leave shrub cuttings for at least a year before even planting out. Left in a sheltered spot I find the extra time gets better results and they establish more quickly if larger. I take off flowering heads in the first year as doing so seems to help the root system grow bigger and stronger. Most plants bought in GC's and shops are at least 2 yrs old, some older. As for the Aluminum, I'd get that in the planting hole when planting. You can add some to the pot when they are established to speed the process, but they need a really good root system first to maximise the benefit.