Minecraft wiki entry for Chorus_Flower, associated text: The smallest possible fully-grown chorus tree (assuming the growth is not disturbed) would have only 5 chorus plant blocks, and the tree (including the flower) would be 5 blocks high. The largest possible tree would be 22 blocks high.
When flowers reach age five, breaking them and replanting them on the same chorus plant block (even on a different face) can allow the plant to grow further.
There is a chorus flower like mob that was featured in the preview for the Echoing Void for Minecraft Dungeons.