The Vegetitan walks like a man, yet has the ability to transform itself into a forest - this shapeshifting takes several minutes, and when complete, where once stood an enormous green man there is instead an expanse of trees, shrubs, and grasses. 
In either form, the Vegetitan maintains a symbiotic relationship with the sproutlings which bud off of its body in pods; these sproutlings - some call them vegepygmies - are smaller than man-sized and of average intelligence. Typically a party of sproutlings is armed with wooden spears and short-bows, and they will fight to defend the Vegetitan, who is their parent and god. When the titan is a forest, they live under the boughs of his trees; when he is a gargantua, they climb over his surface like so many lice and even prune the Vegetitan of dead or worm-nibbled leaves. 
Although it is intelligent, the vegetitan rarely speaks, instead using its booming voice to intimidate enemies or warn animals away from a wildfire. If forced to defend itself, the vegetitan wield both its obvious physical prowess and plant-related magic with aplomb. 
 The vegetitan's shapeshifting abilities conform automatically to the region in which it finds itself; deciduous trees, pines and evergreens, cactus, a field of wheat, magnolias and swamp-moss, etc.
 The gargantua is charged with life-magic, and eating a handful of his leaves or bark may (25% chance) act as a superior healing potion (1d12hp); there is also a chance (10%) that the leaves selected are poisonous. The Vegetitan may spawn potion-fruit at will if it benefits him to do so, though he himself cannot partake of these potions.
 The Vegetitan has 25HD (30HD in Spring) and the magical ability of a ninth-level caster; all of its spells should be plant-focused or reskinned spells which then appear to be plant-focused (ie fireball is instead an exploding ball of rose-thorns, etc). In times of absolute crisis, the Vegetitan may force himself to create a multitude of sproutlings; for each HD the Vegetitan sacrifices, 2d6 sproutlings are immediately spawned.
|"And this one time, we found a spaceship from the future!"|
"SHUT UP, SPROUT."