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).
All hydrangeas love water. Hydrangea leaves sag when the plant is too dry, telling you they need water. The leaves also go limp in midday heat, so wait until evening to see whether they recover before you water them. Whether to fertilize is a touchy question with hydrangeas.