I have an old rosemary bush that looks like a mini tree trunk where it leaves the soil. After years of pruning, it stands about four feet high and the green leaves appear from about one foot up from the soil.
How high up from the ground would it be safe to prune it without killing it or shortening its life? I'd like to clear it from the ground so that I can grow plants below it (that would then get some light) but would it be a good idea to have about 3 feet of plain 'trunk' before the green bush starts? Or would this lead to problems getting nutrients and water from the soil to the leaves?