The bug

When trees, kelp, bamboo, and huge mushrooms generate near biome boundaries, they will generate rough edges on chunk boundaries instead of generating together with the other plants near the biome boundary. Kelp and bamboo will also generate strictly within chunks, inside their respective biomes. Some other plants will only attempt to spawn in certain chunks, but they can still spread out of the chunk (which might also be a bug). This can cause ugly world generation on biome boundaries, including odd bee nest and large tree distribution, and patches of jungle that lack trees near a river.

How to reproduce

Use the seed 5878760421836343227 and teleport to 702 82 652 to go to a river that caused patchy plant generation in a bamboo jungle (and a lot of them nearby).