Sierra Azul Open Space Preserve: Bald Mountain and Mt Umunhum Area

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The Bald Mountain staging area in Sierra Azul Open Space Preserve opened relatively recently, in 2014, and facilitates trail exploration near Mt Umunhum. This hike was a first-time visit to the area and featured spectacular views and a nice variety of wildflowers.

The hike was basically two out-and-back hikes going in opposite directions from the staging area, denoted by the orange dot on the GPS track. The staging area is located on Mt Umunhum Rd about 1.6 miles from the junction with Hicks Rd.

GPS track

GPS track

From the parking area there is a dramatic, close-up view of Mt Umunhum and the iconic radar tower. I always appreciate when there is a fantastic view from a trailhead and consider it to be kind of a good omen for the rest of the hike. Loma Prieta and El Sombroso are also visible from the parking area. I had hiked to El Sombroso on two previous occasions when hiking through Sierra Azul Open Space Preserve. Also, I think this is the closest I’ve been to Loma Prieta, for which the Bay Area’s 1989 magnitude 6.9 earthquake was named.

photo of Mt Umunhum viewed from the Bald Mountain staging area

Mt Umunhum viewed from the Bald Mountain staging area

I first hiked out to Bald Mountain, a grassy knoll with fantastic views of the Almaden and Coyote Valleys and the nearby peaks of the Santa Cruz Mountains as well as the Diablo Range. Almost before I exited the parking area I started to see bright chaparral clarkias (Clarkia affinis) among the grass.

picture of chaparral clarkia near the Bald Mountain staging area

Chaparral clarkia near the Bald Mountain staging area

Along the trail there were poppies, blue-eyed grass, yarrow, blue dicks, lupine, sticky monkeyflowers, hillside morning glories, silver puffs, lots of smooth vetch, and some manzanita. About halfway out to Bald Mountain I saw the first of several butterfly mariposa lilies (Calochortus venustus).

image of butterfly mariposa lily

Butterfly mariposa lily

A short distance later I noticed a low-growing plant with colorful red pod-like structures. I don’t recognize the plant, but it looks like it could be a low-growing form of manzanita. I thought it was rather pretty.  (Update: the red pods are galls.)

photo of colorful plant, possibly manzanita

Colorful plant, possibly manzanita

I also passed a snake stretched out across the trail, still but forming a wiggly line. I walked past it carefully in order to not startle it. Later a garter snake scooted off the trail into the grasses.

The trail reaches the summit of Bald Mountain after a very modest 50-foot climb, and there is a very small loop near the end of the trail. From the summit area there are essentially 360-degee unobstructed views, including the south end of San Francisco Bay, Mt Hamilton, the East Bay hills, Almaden Reservoir, Mt Umunhum, and several ridges of hills to the south.

picture of view of hills south of Bald Mountain

View of hills south of Bald Mountain

After enjoying these views I returned to the staging area and continued up Mt Umunhum Rd behind gate SA08. About 0.3 mile up the road, at the highest point of the hike (2400 feet elevation) the trail called Barlow Rd goes off to the right. Barlow Rd is mostly downhill, descending to 1700 feet where there is a T intersection with Woods Trail, a designated portion of the Bay Area Ridge Trail. The main descent has a grade of almost 15%.

Elevation profile

Elevation profile

Barlow Rd traverses and winds mostly down a steep hillside, passing different plant habitats and some pretty views. Near the beginning of the trail I noticed patches of short plants with puffy white flowers: slender cottonweed (Micropus californicus).

image of slender cottonweed characterized by small white puffy ball-shaped flowers

Slender cottonweed is characterized by small white puffy ball-shaped flowers

In the shaded areas there were quite a few Fernald’s irises and white blue-eyed Mary. Where there were breaks in the chaparral there were nice views of San Jose. Almost all along Barlow Rd there were beautiful blue-purple larkspurs (Delphinium); there are several possible species, and I’m not sure of the specific identification.

photo of beautiful blue-purple larkspur along Barlow Rd

Beautiful blue-purple larkspur along Barlow Rd

There was also a paler type of clarkia, I believe slender clarkia (Clarkia gracilis).

picture of slender clarkia

Slender clarkia

In a few places there were views, seemingly almost straight up, of the Mt Umunhum radar tower. Along shady hillsides there were globe lilies and red larkspur. Quite a few butterflies were busy feeding and flitting past me. Eventually a California sister (Adelpha californica) paused long enough for me to get a photo.

image of California sister butterfly

California sister butterfly

In several places I saw ball-like flowers that reminded me, in some ways, of purple sanicle but with the spikes developed into mini-blossoms. After studying my pictures I think they are tomcat clover (Trifolium willdenovii).

photo of close-up view of tomcat clover

Close-up view of tomcat clover

I was rather startled to see some large thistles that were almost red in color. They are called Venus (or red) thistles (Cirsium occidentale var. venustum). Note the wispy, cobweb-like threads on the involucre (the spiky ball-like structure below the flower head).

picture of Venus thistle along Barlow Rd

Venus thistle along Barlow Rd

From the top of the rise in the trail, at about 2.9 miles, there was a great view of Jacques Ridge in nearby Almaden Quicksilver County Park, with Hicks Rd visible.

image of Jacques Ridge in nearby Almaden Quicksliver County Park

Jacques Ridge in nearby Almaden Quicksliver County Park

Along the long descent I saw some distinctive thistles with many pale purple flower heads on each branch. Having more than 5 flower heads identifies them as slender-flowered thistles (Carduus tenuiflorus).

photo of slender-flowered thistle, with many flower heads on each branch

Slender-flowered thistle, with many flower heads on each branch

A special find on the lower part of the trail was a distinctive third type of clarkia, red ribbons (Clarkia concinna). The three-lobed petals are quite unusual.

picture of red ribbons

Red ribbons

I also saw pipestems, paintbrush, and some woodland stars. Once I reached the junction with Woods Trail I retraced my path to the Bald Mountain staging area.  As I descended Mt Umunhum Rd from Barlow Rd I had a nice view of Bald Mountain, with just a hint of the distant views I’d enjoyed from its summit.

image of Bald Mountain viewed from Mt Umunhum Rd

Bald Mountain viewed from Mt Umunhum Rd

This was a delightful hike with spectacular views and a nice variety of spring wildflowers.

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