Do Not Touch Sakura Branches (桜の木に触らない - Sakura ni sawaranai)
The absolute golden rule of cherry blossom viewing: you must never touch, shake, climb, or break the branches of cherry trees. Sakura are incredibly delicate, and physical contact can spread diseases that kill the tree.
Based on the ancient proverb: 'Only a fool breaks cherry branches, only a fool leaves plum branches untrimmed.' Torn bark introduces deadly fungi, meaning touching literally threatens the life of these century-old trees.
Never pull branches down to force a selfie. Avoid pinning sheets down directly on top of exposed roots, as stepping on them prevents the tree from absorbing nutrients.
What is a strictly forbidden breach of etiquette when viewing cherry blossoms?