Penny Mac Mophead Hydrangea. Penny McHenry of Atlanta introduced this cultivar to the Hydrangea world and everyone has grown to love it. She is singularly responsible for the formation of the American Hydrangea Society, where her enthusiasm was felt by all. This selection has a compact habit with medium sized heads. The flower can be blue or pink depending on the amount of aluminum in the soil, not the pH as many teach. Aluminum induces "blueness;" whereas, a lack of it will induce "pinkness." Of course with a more acidic pH, aluminum is more available. If pruning is needed, do it immediately after flowering as the plant will have time to put on new growth that will set flower buds for the following spring. So that flowering is not affected, try to prune at or before early August.