Willson Peak

Poppies atop Willson Peak

8 miles loop, 1950 feet elevation gain
Difficulty: Moderate
Access: Paved but narrow road to trailhead, Henry Coe State Park entrance fee required

Willson Peak's green grassy ridges, wide-ranging views, and explosively flowery serpentine soils make this tallest peak in the southern half of California's Henry Coe State Park one of the better spring hikes in the San Francisco Bay Area. Hikers who tackle this peak, which has a myriad of paths leading to its summit, many quite steep, will find beautiful floral displays of poppies and other California spring flowers each April in the peak's unique serpentine soils. The views into this relatively wild corner of the San Francisco Bay Area are also worth making the trek out. There are three major trails leading from the Hunting Hollow Trailhead near Gilroy to the summit of Willson Peak: the Steer Ridge Trail, the Jim Donnelly Trail, and the Middle Steer Ridge Trail. I'll describe a hike that takes the steep Middle Steer Ridge Ridge up and returns via the gentler Jim Donnelly Trail that is packed with views and pretty oak and grassland scenery throughout. This hike is best in spring; it can be muddy in winter after rains and is typically very hot and less pretty in the summer.

The hike starts from the Hunting Hollow Trailhead just outside Gilroy. To reach the trailhead, I left Highway 101 in Gilroy at exit 357 and headed east on Leavesley Road. I followed Leavesley Road across farmland for 1.5 miles and then turned left onto New Ave; following New Ave north for a half mile, I then turned right onto Roop Road and followed it into a little canyon. Roop Road soon intersected with Leavesley Road again; I turned left at this junction, which kept me on Roop Road. Roop Road began following a creek valley into the Diablo Range and became Gilroy Hot Springs Road. At a junction with Canada Road, I stayed left to continue heading towards Henry Coe State Park; a mile later, I arrived at the Hunting Hollow Entrance to the right of the road. There was a massive parking lot here with room for at least 50 cars. This is quite a popular trailhead, as its one of just two access points into the vast Henry Coe backcountry that is open year-round. On a nice April Saturday morning, I arrived to a full parking lot and took the very last spot just after 9 AM.

I followed the Hunting Hollow Trail, a road trace, from the large parking lot. The trail immediately crossed the main creek in Hunting Hollow. During my May visit, there was barely any flow in the creek so crossing was quite easy, but in times of higher flow (such as shortly after storms) this crossing (and the four subsequent creek crossing) may become challenging or impassable as there are no bridges. I immediately came to the junction with the Steer Ridge Trail after crossing the creek: this is the most direct and steepest route to the summit of Willson Peak, which I would skip that day. A tenth of a mile later, I passed the junction with Jim Donnelly Trail, which I would follow on my return. 

Crossing the stream in Hunting Hollow

I continued forwards on the Hunting Hollow Trail for the initial two-thirds mile of the hike, crossing the creek five times total. While the trail at times passed through forest, long stretches of the trail passed through grassy clearings that provided nice views of the surrounding green hills. Every now and then, I would come across patches of blooming wildflowers in the meadows bringing brilliant colors to the already verdant grasses.

Grassy clearings in Hunting Hollow

At just under two-thirds of a mile from the trailhead, in a clearing with a windmill, I came to a junction with the Lyman Wilson and Middle Steer Ridge Trails, which split off to the left from the Hunting Hollow Trail. I made the left turn here to leave the Hunting Hollow Trail and immediately encountered a second fork in the trail, where the Middle Steer Ridge split off to the left and the Lyman Wilson Trail headed right. While both of these trails can lead to the summit of Willson Peak, I chose to the take the left fork for the Middle Steer Ridge Trail.

Windmill

The Middle Steer Ridge Trail was a lovely single track trail that initially traveled through the wooded bottom of a valley, passing a junction with a connector trail to the Jim Donnelly Trail that headed to the left and uphill at 0.8 miles. In spring, these woods are especially lovely, with wildflowers dotting the forest floor.

Spring wildflowers

Starting at the one mile mark of the hike, the Middle Steer Ridge Trail began a steady, switchbacking ascent of its eponymous ridge. This marked the start of this hike's long and somewhat arduous climb, with about 1600 feet of ascent over the next 1.7 miles. The early switchbacks carried the Middle Steer Ridge Trail up through a forest of lichen-draped trees. Although there were trees around, foliage cover was sparse enough that I could see the surrounding ridges from the trail.

Lichen hanging off trees

After some initial switchbacks, the trail started on a more direct route along the spine of the ridge, ascending constantly and relentlessly as it climbed up the grassy ridge underneath the canopy of outstretched oaks. This stretch of the trail was very scenic in spring, made even more enjoyable by the fact that the Middle Steer Ridge Trail was a single track trail rather than the typical dirt road trace that's found throughout the Bay Area.

Grassy trail through the oaks on Middle Steer Ridge

As the trail climbed, the oaks became sparser. At 1.7 miles, the trail emerged into a grassy clearing on the ridge, with a brief respite from the steep climb. When the trail began climbing in earnest again, the ridge was mostly exposed, with green grass everywhere and only occasional old oaks dotting the landscape. This is one of my favorite types of Bay Area scenery and I found Middle Steer Ridge on that April weekend to be an exemplar of what I find so beautiful about spring in California.

Big oak on Middle Steer Ridge

As the tree cover dissipated, sweeping views began opening up to the southeast, first encompassing other ridges of the Diablo Range and soon reaching to the distant Gabilan and Santa Lucia Mountains. On a clear day, Monterey Bay and the Pacific Ocean should come into view, but unfortunately some ground-level haze on the day of my hike obscured whatever ocean views might be found on Willson Peak.

Middle Steer Ridge Trail

At 2.3 miles into the hike, the Middle Steer Ridge Trail passed a junction with the Bowl Trail, which split off to the right. I stayed on the Middle Steer Ridge Trail, which went through the steepest pitch of the hike right after this junction, and continued following the trail until it topped out atop a grassy knoll with sweeping views at 2.8 miles. Here, views to the north of the mountainous interior of Henry Coe State Park unfolded. Past this knoll, the trail descended just slightly to intersect with Steer Ridge Road, a wide dirt road trace running along the crest of the main ridge.

View out to the Gabilan Range and Monterey Bay from Middle Steer Ridge

I turned right at the junction with Steer Ridge Road and followed it east and gently uphill for a fifth of a mile through rolling grasslands to the junction with the Willson Peak Trail at 3 miles, which was just short of the high point on Willson Peak. In the V between the split of these two trails was a patch of serpentine soil that becomes the hike's crown destination in spring. This nutrient-poor patch of land is unable to support the grasses that cover the rest of the mountain, providing an opportunity for wildflowers to latch on and bloom in abundance. This small patch of serpentine soil was blooming with brilliant colors during my visit, with orange California poppies mixed with yellows, whites, and purples in a spectacular floral display.

Loma Prieta from the summit of Willson Peak

I followed the Willson Peak Trail for a hundred meters from the serpentine soils to the true summit of Willson Peak, which had fantastic wrap-around views, but I backtracked to the wildflower display for lunch as that was the true highlight of the hike. The views from the serpentine wildflowers was excellent. To the northwest, I could see to Loma Prieta and the Santa Cruz Mountains; while a low hill blocked any potential views of Monterey Bay to the west, I could still see the Gabilan and Santa Lucia Mountains to the southwest. The Steer Ridge Road continued following the grassy, oak-dotted ridgecrest to the southeast, with the Diablo Range near Hollister rising in the distance. The Diablo Range has a notably scenic collection of higher peaks near Hollister, although as far as I can tell there's no name for the grouping of these mountains and they're largely inaccessible on private land.

Diablo Range views from Willson Peak

Serpentine soils are quite common throughout the California Coast Ranges and especially in the Diablo Range, where such soils surround San Benito Mountain, the range's highest peak. Serpentine soils are formed from weathering of ultramafic rock, which is low in silica content and often lacks the nutrients necessary for life but is rich in iron, magnesium, and other metals; due to oxygen content in the atmosphere today, ultramafic rocks are rarely formed in volcanic events and only form in the mantle, where they can sometimes be brought to the surface by plate tectonic events. This is what has happened in California: the convergent boundary between the North American Plate and the Pacific Plate (and previously the Farallon Plate) has surfaced ultramafic rock that formed deep underground. Ultramafic rock- and thus California's serpentine soils- also frequently carry the mineral chrysotile, the soft, fibrous mineral that we know as asbestos. High soil asbestos content in the soil has caused periodic closures of San Benito Mountain in the southern part of the Diablo Range, although such problems have not been reported in Henry Coe State Park, where serpentine soils are instead positively associated with their prolific wildflower blooms.

Wildflowers blooming in the serpentine soils atop Willson Peak

After enjoying the views and the wildflowers, I began my journey back, initially returning from the direction I came along the Steer Ridge Road down to the junction with the Middle Steer Ridge Trail. For the descent, however, I chose to take Steer Ridge Road and the Jim Donnelly Trail down instead: this was a longer but gentler route that would save some wear and tear on my knees. Hikers looking for a shorter trip can return down the Middle Steer Ridge Trail and cut about 2 miles off the hike, but I chose to continue onwards along Steer Ridge Road.

Steer Ridge Road undulated along the grassy crest of Steer Ridge, delivering constant and lovely views, especially to the northeast into the deep heart of the chaparral-dominated Diablo Range. Some distant ridges still appeared charred during my hike, a reminder of the effects of the 2020 SCU Lightning Fire, a massive conflagration of the Diablo Range between Altamont and Pacheco Passes that at the time of writing remains the fourth largest wildfire in California history. 

After initially dropping gently to a saddle, Steer Ridge Road climbed to a lower bump at 4.2 miles. Leaving this peak, the trail made a turn to the southwest and began a steeper descent. Here, views from the grassy ridge encompassed Hunting Hollow to the northwest, made prettier by patches of poppies that popped up around serpentine outcrops. I ignored a turnoff for the Spikes Jones Trail on the right at 4.4 miles and descended along Steer Ridge Road until reaching the junction with the Jim Donnelly Trail at 4.8 miles.

View from Steer Ridge towards Mount Hamilton

I turned left at the Donnelly Trail junction to follow the single track Jim Donnelly Trail for the rest of the descent. The Donnelly Trail had a gentler grade than Steer Ridge Road and used broad switchbacks for the initial descent down a grassy slope. There were pretty views from here over Hunting Hollow and towards the Hollister area Diablo Range peaks; a small pond lay below in a grassy bowl. After passing the pond at about 5.5 miles, the Donnelly Trail followed a ridge and descended gradually but steadily towards the floor of Hunting Hollow, with plenty of switchbacks to ameliorate the downhill grade. The trail generally stayed out in grassy meadows with views, but after passing a junction with the connector trail that led to the Middle Steer Ridge Trail at just under 7 miles, the Donnelly Trail returned to oak woodlands for the remainder of the descent. The Donnelly Trail rejoined the Hunting Hollow Trail just a tenth of a mile from the Hunting Hollow Trailhead, so I turned right at the junction and followed that gravel road back to my car.

Looking over Bills Hill and Hunting Hollow from the Jim Donnelly Trail

I enjoyed this hike up Willson Peak a lot. The views are wonderful, the wildflowers are explosively colorful in spring, and there's a good mix of single-track trails to break up the monotony of the road traces that are so common throughout the Bay Area. This is perhaps the best day hike in Henry Coe State Park, which is itself the largest protected area within the Diablo Range. While these hills may be less fun on hot summer days when the grasses have turned brown, they are a delight when hiked at the right time of year.