I like this idea, we have a plant tree why not a bone or rock tree? Here’s some traits that could go with them:
-Bone/rock armor: Grown layer of natural armor over body, but is encumbering.
-Tunneler: With hardened hands, they act as a natural pickaxe, and cost less energy.
-Earth eater: Can now eat/adsorb rocks/bones for nutrition/energy as well as bonus armor.
-Rock throw: At cost of energy can throw a chunk of earth. Aoe type.
-Heavy: Can’t be knocked back or stun by most things, but also really heavy. Avoid water, or small cars
-Rock solid: Very difficult for things to penetrate body, resistant to most types of attacks that inflict some kind of status attack