I inherited an old, tall ‘Red Robin’ about 10 ft high. The lower branches have few leaves and look as if they won’t grow any new shoots. The upper branches have only a few healthy leaves and a lot of them drop off. Is it too tall to heavy prune. I am worried I won’t get any new growth if I do this but I can’t see a light prune helping. It would be very difficult for me to dig out Any advice welcome.