The Boneleaf is a monster in Heroes of Horror, D&D 3.5 page 143. The creature that the party generally encounters is actually a part of a much larger, subteranean monster that has 1D6+6 other similar outcroppings above ground.
To quote Heroes of Horror:
A boneleaf functions as an independent creature, but it is only a portion of a much larger whole. While boneleaves are encountered singly, they are not actually alone. If boneleaves are present in a given area, there are always 1d6+6 of them in the region. They are considered solitary creatures because each boneleaf in the group remains anywhere from 100 yards to a mile away from its nearest fellow. All the boneleaves in a group are in fact portions of the same creature, connected by miles of underground nerves. Anything one boneleaf experiences is known to all of them, so characters who encounter a second boneleaf after defeating the first will find it anticipates their tactics and abilities.
The monster is a large aberation, with a CR of 6. Even though it is not a plant, it has some plantlike features. Another quote from HoH:
Although a boneleaf is not a plant, it has many traits also possessed by plants. A boneleaf is immune to magical sleep effects, paralysis, stunning, and mind-affecting spells and abilities (charms, compulsions, phantasms, patterns, and morale effects). It has some fortifi cation against critical hits; 50% of all critical hits function as normal strikes. Boneleaves so closely resemble plants that a character must make a DC 15 Spot check to realize the boneleaf is anything more than a normal copse; failure indicates the character comes close enough for the creature to attack with its extended reach before he suspects anything is amiss.
I am planning an encounter somewhat in advance, but expect that by the time the party will face their first Boneleaf as a group of 5 7th level players. The plan is that the party will face another creature more suited to their level, but as it reaches a certain HP threshold it will try to get away. If it succeeds, and the players decide to follow it, they will find the creature licking its wounds against a tree. If they approach it, they find out that this was an illusion made by the Boneleaf to lure them closer to it, and the battle with the boneleaf begins (and the first creature gets away). The party consists of one Wizard, one Rogue, one Dread Necromancer, one Barbarian and one Cleric. I plan to locate the 'real' monster beneath the village where the players will be residing for the duration of the adventure. It would seem that the entire monster itself has no stats, for as far as I can see at least. Only these above-ground outcroppings have a statblock, and there is nothing I can find about the creature itself.