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).
Phosphorus is needed for bone and tooth health just like calcium, but it is also a vital part of metabolizing energy. Without phosphorous, your body can't turn food into energy and strength. It also is essential to kidney and liver function. Foods high in phosphorus are usually also high in protein.