Mortar Rock takes its name from the many holes worn in these hard lavas by Native American women pounding and grinding acorns and other seeds into meal. This staple food could be stored and later cooked into cakes or porridge.
Native Americans also used many of the other plants in this park. California bay trees (Umbellularia californica), relatives of avocados, provided oily, nutritious nuts. Their pungent leaves, like those of mugwort (Artemisia californica) helped keep insects out of food stores.
Big, glossy seeds of California buckeye (Aesculus californica) were mashed and used to stun fish. In lean times, they could be leached of their poisons and eaten. Blue elderberry (Sambucus mexicana) branches were easily hollowed out to make flutes and clappers. The soft pith helped kindle fires. The berries were eaten along with many others, including rose hips and berries of toyon (Heteromeles arbutifolia). Other plants were used in baskets, clothing, dyes and medicines.