Harvest before lightning when money safety matters; wait only when you are deliberately testing a permanent-tree or higher-value run, and never rely on an unsupported timer.
Decide when to harvest while a tree grows and lightning risk is possible.
For active grinding, secure small harvests quickly and sell them; for long-term garden building, let only selected trees keep growing while you accept lightning risk. Roblox confirms the loop and lightning threat, but exact strike odds and safe height thresholds are not official.