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, being an essential plant nutrient, finds its major use as a constituent of fertilisers for agriculture and farm production in the form of concentrated phosphoric acids, which can consist of 70% to 75% P 2 O 5.