So I admit that this one is being suggested mostly because it is creepy. This has been somewhat inspired by your Necrobotany ideas, Zaydos. I hope you don't mind. If you do, just say the word and it's gone. :)
Once, a necromancer thought to turn her unique talents to good. She thought she could create a tree that would turn the bodies of the dead into food for the population of her starving homeland. Using her knowledge of disease and death, she devised the Tree Of Salvation, her crowning achievement. Not only would it quickly turn the deceased into a solution to the food problem, but its apples would also keep the population safe from plague! It wasn't until she had convinced her home town of its perfect safety, however, that she learned the terrible mistake she had made when she imbued the fruit with necromantic magic. Some stories are told of explorers stumbling upon a wonderous grove of apple trees growing in the ruins of an abandoned town. It was eventually burned down with the strongest of fire magic, but not before some foolish man took a few apples to save his dying mother...
Tree of Salvation(The Devil Tree)
Take a deep breath and you'll find yourself overcome with the delightful scent of crisp autumn apples and the faintest hint of cinnamon. Gaze upon this tree and find yourself dazzled by its canopy of fiery colors. The apples that hang alluringly from its slender branches are the perfect shade of red, shot through with tiny flecks of golden yellow. The tree itself stands 10 feet tall, its fruit just within reach.
The fruit of this tree is highly nutritious, instantly restoring 1 hp for every apple eaten. The apples also cure any non-magical poison and diseases. The apples also seem to be seedless! Unfortunately, the tree carries a dark secret. The tree does not reproduce through seeds. Instead, a disease grows in the apples that infests the bodies of anyone who eats them. (DC 15 fort save (3.5e)/ DC 13 Con save(5e)) On a failed save, the disease provides a +3 bonus(3.5e)/advantage(5e) against diseases and poisons until winter nears its end. Then, the disease begins to act, assaulting the brain of its host. The victim is compelled (Will DC 17/Wis DC 15) to find suitable ground for planting and linger there. Once this phase begins, the subject begins taking damage as though starving to death, no mater how much they eat or drink. No amount of hunger overcomes the compulsion, however.
Bugs and animals shun the corpse and, 1d6+3 days after the host's death, a new tree begins growing from the head of the deceased, using the body of the dead as nutriants.