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).
Phosphates are also used in enemas as laxatives. Most people get plenty of phosphorus in their diets. Sometimes athletes use phosphate supplements before competitions or heavy workouts to help reduce muscle pain and fatigue, although it's not clear how much it helps or if it improves performance.