Los Osos Oaks State Natural Reserve features ancient sand dunes covered with centuries-old coast live oak trees. According to botanists, five major plant communities thrive within the reserve. They are coastal sage scrub, central coastal scrub, dune oak scrub, coast live oak forest, and riparian (streamside). The oak communities exist close to each other, but each has its own character. The oak scrub has dwarf oak trees growing on the ancient (relict) sand dune. Though they are coast live oak trees, they rarely grow more than six to eight feet tall. The larger coast live oaks are located where the soil is moister. These giants can grow to 25 feet in height. Their massive trunks and gnarled branches twist into all sorts of fantastic shapes.