This is good stuff. I might use this in a world im thinking up right now. plant traits are:

Plant Type
This type comprises vegetable creatures. Note that regular plants, such as one finds growing in gardens and fields, lack Wisdom and Charisma scores (see Nonabilities) and are not creatures, but objects, even though they are alive.

Features
A plant creature has the following features.

8-sided Hit Dice.
Base attack bonus equal to ¾ total Hit Dice (as cleric).
Good Fortitude saves.
Skill points equal to (2 + Int modifier, minimum 1) per Hit Die, with quadruple skill points for the first Hit Die, if the plant creature has an Intelligence score. However, some plant creatures are mindless and gain no skill points or feats.
Traits
A plant creature possesses the following traits (unless otherwise noted in a creature’s entry).

Low-light vision.
Immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
Immunity to poison, sleep effects, paralysis, polymorph, and stunning.
Not subject to critical hits.
Proficient with its natural weapons only.
Proficient with no armor.
Plants breathe and eat, but do not sleep.
Thats from the srd (www.d20srd.org). hope it helps.