Growth Mechanics of Sugar Cane
Sugar cane grows only when the block above it is empty. Sugar cane grows on its own up to a height of three blocks.
The Random Tick Aging Counter
Each random tick adds one to the age of the top sugar cane block; at age 15 a new block grows on top and the age resets to 0.
Our companion Seed Map displays waterways, rivers, and coastal terrain suitable for exploring crops across your seed.
Sources
Read from the official 26.3 server jar (SugarCaneBlock.randomTick).