I have a fantastic 20+ year old Rosemary which has even produced flowers on Xmas day in our garden in the north west of england. BUT the stems are now as gnarled as an old olive tree and although it is producing lots of growth at the very top, the trunk is now looking a bit bare and sorry for itself. I need to prune it dramatically but am afraid of killing it. Has anyone any ideas about how to go about this pruning? Shall I be bold?
Don't be bold with pruning Rosemary! If you prune it back to old wood it maay well not produce any new shoots. I would prune it back to about 1 inch (2.5cm) above the old wood. This may cause it to produce shoots on some of the old wood stems.