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).
Hydrated lime is not a necessary mortar ingredient. You can make mortar with just Portland cement, sand and water. The mortar that I used to permanently attach the brick and stone to my patios did not contain any hydrated lime. But adding hydrated lime to the mortar mix can be beneficial. The plasticity or workability of the mix will improve. When hydrated lime is added to the mix, the sand and the cement do not separate.