Very sparse bottom, bushy top....in mid summer season, what can I do to fill in the bottom. Someone suggested I cut 4-5 inches across the top....will that work?
If you prune the entire shrub back close to the ground now, you will remove the wood that contains the flowering spring buds and you will have no flowers next spring. You could decide to cut it back completely next spring after it blooms so that you can enjoy the flowers. If the shrub is healthy, it will respond with strong new growth that will need to be periodically pruned for the health and form of the shrub.
In rejuvenation pruning, 1/3 of the oldest branches along with diseased or dead branches are removed every year. This results in a gradual improvement of shrub size and form without sacrificing its presence as an anchor plant. This pruning would take place after spring blooming is finished.