Raise Dead As Tree (5th Level Spell)Reversible, Duration: Permanent, Range: touch
When cast on a corpse lain on open soil, causes a tree to sprout and grow to full size on the spot. The soul of the slain victim will inhabit the tree as long as the victim died within 3 days per level of the caster. The tree is immobile and mute except under the influence of magic, but while animated, can earn experience, becoming able to move its limbs at 2nd level, speak at 3rd level, and walk at 4th level (but must bury its roots in soil to sleep.)
The reverse is Slay Tree, which pretty much does as it says.