Mountree possess a large hardened soil shell that is similar to a tortoise's. On the shell are three small trees that seem to be planted on small, mud-like hills, as opposed to the three shoots that appear on a Forestone's back. This soil-like shell is brown in colour and contains a few small yellow dots towards the middle that have the appearance of small pebbles. Its lower body is a soft, olive-like color that is known to be a weak spot. The large shell gives them a lot of protection from even the strongest of enemies. It has clawed, stumpy legs that make it exceptionally hard for it to run fast or long distances. The rest of its body is green in color, so that it blends in more with the surrounding forest flora. Its head possesses three small horns that give it an incredible boost in using head-smashing moves. Its eyes are marine blue which gives a less intimidating look to it, to show that it is the guardian of all forest-dwelling Pokémon.
Mountree has an exceptionally hard shell, even harder than granite. However, the weight of its hardened soil-like shell make it very slow, although its speed can increase when it uses Rock Polish. The horn and armor on its head make it capable of using powerful moves that require the use of a Head Smash. The small shoots on its back are actually trees, and they can shoot powerful sharp edged leaves at opponents from them.
Mountree is extremely brave and will attack foes that may be much more poweful than itself. It is very protective of its home forest and will defend it at all costs. Mountree will never leave its forest. It often scares away forest Pokémon that may attempt to nest on its shell.
Mountree will always live in the forest that it was first born in. At this point of its life, it will most likely be the most strongest Pokémon in the whole forest and thus will act as a guardian for all the forest life.
Mountree guards its forest from any danger, willing to risk its life to help those in need. Its shell is as hard as granite.