Del Mar Mesa Preserve (Vernal Pools, Eucalyptus Grove & Tunnel 4 Trail)

While we visited Los Penasquitos Canyon last November to hike to the Penasquitos Creek Waterfall, we return this time to explore the 8 miles of trails in the Del Mar Mesa Preserve that only legally opened to the public in 2015. The 900-acre nature preserve occupies a mesa that rises to the north. From the Del Mar Mesa Trailhead at the end of Park Village Road, we started our hike on Powerlines Trail, named for the transmission towers that flank the dirt road climbing the north slope of the long Los Penasquitos Canyon. 

At the top of the Powerlines Trail that ends at a gated housing community, we turned right to enter the Del Mar Mesa Preserve along The Fire Road. Walking along the busy trail, we encountered two forks in the main trail. The first fork splits left into a one-way mountain bike trail called Bowtie Rim that rejoins at the next fork where we left the Fire Road to go right toward the Eucalyptus Grove. The tall non-native trees framed the antenna-covered summit of Black Mountain in the distance.

Past the grove of eucalyptus, there used to be a local trail that extended further out onto the mesa, but is now off-limits to create a protected habitat area and wildlife refuge. To the left of the blocked trail is the entrance to Tunnel 4 that leaves the mesa to descend into a narrow canyon alongside it. A forest of scrub oak covers the trail with its thick canopy that gives it its descriptive name. The dark winding trail with banked turns is popular with mountain bikers and several passed us on our hike down.

At the bottom of the shade-filled tunnel, the ground leveled out and opened into a sun-dappled forest with the stream bed of Deer Creek running through it. If we had continued on, we would have reached Deer Canyon Trail that travels west to meet up with The Fire Road and climbs back up to Del Mar Mesa via Cardiac Hill. Without an accurate map, we decided to retrace our steps up Tunnel 4 instead.

The sun was setting as we passed through the Eucalyptus Grove and onto the Fire Road with several pools of water running down the center. They are examples of the numerous Vernal Pools that the preserve was created to protect. These small pools of standing water that only last a few months of the year are a special ecology and provide an important habitat for the local plants and animals of this dry chaparral environment.