Mine is very young, only had her 3 years but it's starting to get to a decent size and the flowers were massive this year. Do you have any organic compost or manure compost to mix in the planting hole? You can also buy mycorrhizal fungi which are useful for woody plants (not ericaceous though) to help establish quicker.
@ukjohnny oh wow, I didn’t even know.. I will share it with my husband who served in the army..thank you 💕.. @ublaszko I mixed mine with compost soil and mulched around it. Will also take notes on other bit.. thanks a lot. 😍💕