For an initial visit to Pleasanton Ridge Regional Park, this was an ideal semi-loop hike. Pleasanton Ridge Regional Park is a currently largely undeveloped open space just west of Pleasanton, including the upper portion of Pleasanton Ridge. There is only one trailhead, at the Foothill Staging Area on Foothill Rd. Various loop hikes are possible, from less than half the length of this one to more than twice the length. Two sections of the park are connected by the City of Pleasanton’s Augustin Bernal Park. The primary highlight is the fantastic views from the ridge-top.
After hiking up to perhaps the main trail junction, intersection #5, I followed a path roughly northwest and slightly below the ridgeline on its west side, mainly on Thermalito Trail. Then I went up to Ridgeline Trail on the ridge-top and continued northwest a short distance into Bernal Park before returning along Ridgeline Trail. The basic semi-loop route was 6.9 miles, plus about 0.6 mile of detours, and a bit over 1800 feet of elevation gain. On the GPS track the orange dot denotes the staging area.
There was a variety of plants in the picnic area at the trailhead, including this interesting-looking native grass less than 6 inches high.
The lower part of the trail passes close to a large patch of poison hemlock (Conium maculatum). To set the scale, the plants are about 5 feet tall, and they have a characteristic lacy leaf pattern.
At the first junction I turned left to go up Woodland Trail, passing Ithuriel’s spear, milk and Italian thistle, blue-eyed grass, and yellow sticky monkeyflower along the way. The trail climbs steadily to intersection #5 and subsequently higher along the contour of Pleasanton Ridge. The outbound route, mainly along Thermalito Trail, is a bit less steep than the return route along Ridgeline Trail.
As the trail climbs from the trailhead, if you turn around you can see I-680 in the valley below. Around intersection #5 there is a pretty view of Sunol Ridge, which runs parallel to Pleasanton Ridge about 1 mile away.
So many trails meet at intersection #5 that I initially left the area on a different trail from the one I intended to take. By the time I got everything sorted out, I had covered about 0.6 mile exploring some of the nearby trails. I intended to follow the arrow to Ridgeline Trail, though I did not realize it at the time. At the next intersection, #10, I followed a short trail toward Olive Grove Trail, then Olive Grove Trail to Thermalito Trail. Along Thermalito Trail I began to see yellow mariposa lilies (Calochortus luteus).
I also passed poppies and yarrow and listened to meadowlark songs, which always make me feel like I’m far away from civilization. There were sweeping views to the southeast, like this one.
You could also look up toward the top of Pleasanton Ridge to see where the route would later lead. After almost 1 mile on Thermalito Trail, at intersection #17 I hiked up a short, steep spur trail to Ridgeline Trail, where I turned left to hike along the highest portion of the ridge-top. In this area there is a single-track trail popular with mountain bikers that goes up and over several hilltops, all almost the same 1500-foot height, while a more level fire road winds around the hills. I decided to follow the bike trail.
After passing over the hilltops I arrived at a gate (intersection #19), where the trail drops down the east side of the ridge-top and enters Augustin Bernal Park. In this shady area there was more yellow sticky monkeyflower, a few purple Chinese houses (Collinsia heterophylla), and some elegant clarkia (Clarkia unguiculata). I turned around at the intersection of Ridgeline and Thermalito Trails. When I returned to the hills at the top of the ridge, I paused to savor the views. Roughly perpendicular to Pleasanton Ridge was a nice view over the city of Pleasanton and across several small reservoirs toward Los Vaqueros Watershed – note the windmills on the skyline – and Brushy Peak, just out of view to the right and about 15 miles away.
Almost due north, Mt Diablo was clearly visible about 17 miles away.
Shortly after I passed the junction where I’d joined Ridgeline Trail there was one last small rise, with spectacular views to the southeast, with the Sunol and Ohlone Wildernesses in the background and the lower portion of Pleasanton Ridge in the foreground.
As I returned along Ridgeline Trail I was startled to see a few clay mariposa lilies (Calochortus arguillosus), the first time I’ve seen two different types of mariposa lily in such close proximity. It was quite breezy, so I had to carefully hold the blossom to keep it still enough for the photo.
Shortly after that the trail passes through a small grove of trees, almost equally spaced. I think they are bay laurel trees.
And just past the grove of trees there is a water fountain next to the trail! There were additional pretty views to the southeast as the trail continued to descend from the top of the ridge. Eventually I reached intersection #10, where I’d branched off earlier in the hike, and retraced my path to intersection #5 and down Woodland Trail to the trailhead. This was a great introduction to Pleasanton Ridge Regional Park, and I look forward to return another time to explore the northern portion of the park.