Plants are a food source that can be eaten by herbivores and omnivores. Plant matter is much more easily obtainable than meat, considering it does not have to be killed before it can be eaten. There are three types of plants that can be eaten; shrubs, trees, and mushrooms.
Trees are a food source that only sauropods and Therizinosaurus are capable of eating. They are easily accessible in the northern and southern portions of Isla Rubzteria, not existing in the central areas. There is a stark difference in the size of the trees compared to the north and south; most of the trees in the swamp are very robust, making the area a prime habitat for browsers, while the trees in the valley are very small, and even all of the trees in the main area are incapable of filling even a baby dinosaur.
Trees also serve the function of providing shelter to flying animals, such as Pteranodon and Microraptor. It is especially common to find the latter hiding in the leaves of a tree, due to how easy a target it is for practically all other dinosaurs in the game. There is, however, an odd glitch that allows a player to climb a tree by jumping repeatedly while pressed against the tree's trunk.
Shrubs (often referred to as "grass" by players) are a very common food source that can fill up various herbivores, and some omnivores. They are found very frequently in the desert and valley areas, though there are only two known shrubs in the northern region of the island. It does not fill up a dinosaur's stomach particularly quickly, at a rate of 8 hunger replenished per bite.
Mushrooms are an interesting kind of food that is edible by various herbivores and all omnivores. They are not common on the map, only found in the mountains, on top of the swamp/desert boundary cave, and dotted on various spires in the southwest. Mushrooms are special and rather dangerous in that they are the only plants capable of giving a dinosaur food poisoning in certain times of the year.
There are three varieties of mushroom; all of which edible in accordance to the seasons. The first variety is edible in winter and spring, found exclusively on top of the various spires in the western half of the valley. The second is edible in spring and summer, and is commonly found in the northwestern mountains at this time. The third and final variety is edible in fall and winter, and is found on top of the swamp/desert cave.