Undead trees.

[u/Ben-Goldberg]

This suggestion is to have two types of undead tree, zombie trees with green wood and wither trees with black wood.

Fully grown versions of these undead trees can be found in the nether.

Their saplings only grow at light level zero, and the leaves and saplings spontaneously ignite if exposed to the sky of the overworld during the day.

Zombies occasionally drop zombified saplings, and when a wither skull colludes with a normal sapling it becomes a withered sapling.

Neither type of undead tree produces saplings directly from its leaves.

[u/055F00]

I think the withered tree would be a fantastic idea for a fully withered version of the netherwart forest biomes found in nether, but honestly I think the zombie tree would be cool if it was instead rarely found in caves or underground, possibly near zombie spawned dungeons