Root. In the computer world, root refers to the top-level directory of a file system. The word is derived from a tree root, since it represents the starting point of a hierarchical tree structure.
Use a fertilizer with high levels of phosphorus. Phosphorus helps to prevent aluminum from creeping into the system of the hydrangea. Choose a fertilizer close to the ratio of 25/10/10 (Phosphorus is the middle number).
When fertilizing hydrangeas, use a fertilizer that has a low nitrogen content. Too much nitrogen, like too much water, makes few or no blooms and large, thick, lush, dark green leaves. Acidify your soil if you want blue blooms rather than pink. Prune hydrangeas in late fall, winter, or spring.