Several ecosystems exist in the park and preserve. In canyons, bay trees and
big-leaf maples form shady groves. Along creeks, several species of willow grow, and cottonwoods are found in a couple areas. On cooler, north-facing slopes, oaks and bays form a forest. On hotter, south-facing slopes,
chaparral scrub of
chamise,
manzanita, and
birch-leaf mountain mahogany predominates.
Douglas-fir, common west of the crest of the Santa Cruz Mountains, can be seen as lone trees above the Rogue Valley trail, and along the Black Mountain trail; they are the only
conifer in the park. Ridges support grassland and scattered oaks. The Open Space Preserve protects the watersheds of West Branch Permanente Creek and its Ohlone Creek tributary. West Branch Permanente Creek begins on the east side of 1,253-foot Ewing Hill, and runs easterly until it reaches the connector from the Chamise and Rogue Valley Trails where an earthen dam forms High Meadow Pond (aka Rogue Valley Pond). Below the pond, the West Branch is joined by 1.7 mile long Ohlone Creek at Deer Hollow Farm and continues on its run (3.2 mile total) to join the
Permanente Creek mainstem 1/2 mile south of Interstate 280. West Fork Permanente Creek and its Wildcat Canyon tributary flow intermittently in summer and fall. Permanente Creek flows year round along the approximately 2 mile stretch in the County Park. The Permanente
riparian corridor is crucial for wildlife survival, providing food and water as well as the ability to migrate through suburban areas relatively undisturbed. Rancho San Antonio is home to native species such as deer, mountain lion and bobcat. The big cats are tracked and thus far have posed no threat to humans. Visitors are warned of the presence of the animals with signs at the entrance to the preserve and various trail map stations. The Rancho San Antonio land preserve is one of the few remaining tracts of land in Silicon Valley where native animals can roam free. Along with deer, other commonly seen animals are California quail, cottontail rabbits, crows, hawks, jays, LBBs (little brown birds), lizards, squirrels, turkeys, voles, white tailed kites, woodpeckers. Less common, reclusive, or seasonal are blue herons, butterflies,
California slender salamanders, coyotes, egrets, frogs, gopher snakes, jackrabbits, newts,
rattlesnakes, skunks, tarantulas.
Star Thistle is an invasive species growing prolifically in the meadows and along sunny trail sides in the park and the preserve. near Permanente Creek in Rancho San Antonio County Park The State's tallest and third largest
California bay laurel tree (
Umbellularia californica), estimated to be over 200 years old, grows in Rancho San Antonio County Park. The tree was protected in 2004 with the addition of fencing and by the removal of a nearby handball court. At the time it was 126 feet tall, its canopy spread was 118 feet, and the trunk circumference was 30 feet. In 1869, the wood of a California Bay Laurel was used for the “Last Tie” connecting North America's first transcontinental railroad. The tree's leaves are highly aromatic and its small yellow flowers bloom between December and April, important to bees at a time when few other plants are in bloom. ==Deer Hollow Farm==