Purisima Creek Redwoods OSP – in search of trilliums

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A recent social media post prompted this visit to Purisima Creek Redwoods Open Space Preserve, one of my favorite preserves on the spine of the peninsula along Skyline Blvd (CA-35).  The 4700-acre preserve is part of the Midpeninsula Regional Open Space District and features beautiful redwood forest, the Purisima Creek Canyon, and wildflowers.

I have hiked in this preserve several times previously, notably as part of my Bay Area Ridge Trail circumnavigation (see here and here) and to explore Irish Ridge.  What was provocative about the social media post was reported sightings of Western trillium (Trillium ovatum) – I think I’d seen one before, but I wanted to see more.  This beautiful wildflower was the highlight of my hike, but was far from the only wildflower I encountered.

photo of Western trillium: highlight of this hike

Western trillium: highlight of this hike

I had been able to inquire about likely locations for Western trillium, and had been provided with specific trail names.  This was quite helpful in planning my itinerary, as there are more than 24 miles of trails in the preserve.  Rather than drive to the lower, western park entrance I used a smaller trailhead along Tunitas Creek Rd; there is informal roadside parking for only about 4 cars near this trailhead.  I determined a basic route of about 8 miles, intended to cover as much as possible of the trails mentioned to me.  Once underway on my hike I added or extended explorations so that my total hike length was 10.8 miles.  The GPS track map shows my route, with the orange dot indicating the trailhead.

GPS track

GPS track

Because I didn’t start at the western park entrance – it’s a longer drive from my house – there was an initial descent down the Purisima Creek Canyon to reach the areas most likely to host trilliums.  Altogether there were about 1600 feet of elevation gain and loss, for an overall average grade of 5.7%.  As shown on the elevation profile, there is very little “flat” area in the preserve.

Elevation profile

Elevation profile

As a side note, I decided to research the proper plural of trillium for this post.  The obvious candidates were “trillia” – which my 4 years of Latin study insisted should be correct – and “trilliums” – which grated on my sensibilities but I found in several online dictionaries; my 1150-page Webster’s Dictionary didn’t even contain an entry for trillium.  Eventually I ran across a blog post in which a commenter explained that trillium is apparently a so-called New Latin term, the type of Latin used for scientific and literary classifications in the last 400 years.  I’m not sure why that would change the form of the plural, but for now I’ll go with “trilliums”.

From the Tunitas Creek Rd trailhead the Grabtown Gulch Trail leads down to the Purisima Creek Trail via two options: the continuation of Grabtown Gulch Trail and Borden Hatch Mill Trail.  I had decided I would go down the latter, so I turned left at the first junction.  Quite soon I was surprised to encounter a California banana slug (Ariolimax californicus) at the side of the trail tread.  I wasn’t surprised to see a banana slug in the preserve, since much of the Purisima Creek Canyon has just the kind of moist environment that banana slugs seem to like, but I was not yet in the moist, lower parts of the preserve.

photo of California banana slug

California banana slug

In fact, in the upper parts of the trail I found a few wildflowers that I associate with shady, but somewhat drier, forest environments.  One was hound’s tongue (Cynoglossum grande).  This individual happened to be in a small spot of sunshine when I came by.

photo of hound’s tongue

Hound’s tongue

After about 0.2 miles on Borden Hatch Mill Trail there is another junction, where Bald Knob Trail leads down to Irish Ridge Trail, the destination for a previous visit to the preserve.  This time I continued down Borden Hatch Mill Trail, which descends 900 feet over 2.5 miles to reach Purisima Creek Trail.  Throughout the higher elevations of this hike I encountered milk maids (Cardamine californica), a delicate early-blooming spring wildflower.

photo of milk maids

Milk maids

In addition I found some forget-me-not (Myosotis latifolia), whose blossoms look similar to hound’s tongue though are smaller, are lighter in color, and have slightly different centers.  Unfortunately, forget-me-nots are non-natives that are considered to be invasive.

photo of forget-me-not


As I continued down Borden Hatch Mill Trail I passed a few fairy rings: several second-growth coast redwoods (Sequoia sempervirens) growing in a ring around the stump of a former old-growth redwood.  These fairy rings are reminders that the area was heavily logged in the late 19th and early 20th centuries, to build and then re-build San Francisco.  Today’s forest is much younger than the original redwood forest, and it is a blessing that so many areas are now preserved as open spaces.

In other places there are large redwoods on the high side of the trail with part of the margin of the root system extending slightly out of the ground to the side.  I think of these as redwood “toes.”  In another place I noticed a stump, without a fairy ring, that had new shoots growing on its top and sides.  These wonderful trees can be resilient about regenerating themselves.

As the redwoods become one of the dominant forest species there are large clusters, almost mats, of redwood sorrel (Oxalis oregana) on the forest floor.  The three-leaf-clover-like leaves are distinctive, and the petals are white to pink in color with beautiful veins.

photo of redwood sorrel

Redwood sorrel

The Borden Hatch Mill Trail tees into Purisima Creek Trail, which runs along the creek for about 4 miles from the western park entrance on Purisima Creek Rd to one of the main park entrances on Skyline Blvd.  It was one of the target trails for finding trillium.  The trail is near the south bank of Purisima Creek, along a fairly steep canyon wall.  This trail is the heart of the preserve, with ferns and other plants and with wildflowers that enjoy a moist, shady environment.

photo of Purisima Creek Trail

Purisima Creek Trail

When I arrived at the junction I knew I was only about 1.3 miles from the lower end of Purisima Creek Trail.  My primary itinerary was uphill, but I decided to explore downhill first.  I figured that the area near the creek would be prime territory for trilliums.  I’m really glad I went downhill because, about halfway down, I found my first Western trillium.  It was a single plant and, if I hadn’t been looking so carefully on the creek side of the trail, I might have missed it.  For one thing, I’d forgotten that the leaves and flower are usually at least 8” high, so I was actually looking for the wrong type of plant.  This close-up shows the three large, deeply veined leaves, the three white petals and three sepals, and six yellow anthers and other reproductive parts.

photo of Western trillium, up close and personal

Western trillium, up close and personal

Besides redwood sorrel, another redwood-associated wildflower is redwood violet (Viola sempervirens).  I saw lots of these pretty flowers below about 1300 feet elevation on my hike.

photo of redwood violet

Redwood violet

There were many types of fern along my route.  I happened to notice this one after I’d turned around at the first trillium and was making my way uphill on Purisima Creek Trail.  This entire plant was about a foot in diameter.

photo of fern along Purisima Creek Trail

Fern along Purisima Creek Trail

There are several small streams that come down the canyon sides to Purisima Creek, including one near Borden Hatch Mill Trail.  Back near this junction I noticed some common horsetail (Equisetum arvense).  The genus Equisetum is considered to be the oldest vascular plant genus, with predecessors potentially serving as a food source for dinosaurs.  It is interesting to contemplate this history while enjoying viewing these plants, which are actually ferns.

photo of common horsetail

Common horsetail

I was planning to hike up Purisima Creek Trail about 2 miles from where I turned around, past Borden Hatch Mill and Grabtown Gulch Trails to Craig Britton Trail.  Along the way the trail crosses the creek several times, including 3 bridges.  I also passed quite a few trilliums and had an opportunity to see more variety in the plants and the flowers themselves.  This picture shows a bit more of the plant, whose main stem was roughly 8” tall.  Unlike other local trillium species, the flower grows on its own stem, which is at least 1” long.  A few of the flowers I found had pinkish petals, either a slight variant or possibly at the later stages of the flowering phase.

photo of Western trillium showing main stem, flower stem, and pinker petals

Western trillium showing main stem, flower stem, and pinker petals

Craig Britton Trail goes roughly northwest past Soda Gulch to Harkins Ridge Trail in the northern part of the preserve.  I hiked in a few tenths of a mile before turning around.  This trail is narrower than Purisima Creek Trail, is open to hiking only, and passes through beautiful redwood forest.

photo of redwood forest along Craig Britton Trail

Redwood forest along Craig Britton Trail

Along Craig Britton Trail I found a few wildflowers I did not see – or notice – elsewhere on my hike.  One example is California blackberry (Rubus ursinus), with characteristic five petals and a small forest of white stamens.

photo of California blackberry

California blackberry

An interesting find was large flower fairybells (Prosartes smithii).  The leaves remind me of Solomon’s seal – perhaps they shouldn’t, since they are alternate rather than opposite – but in any case the flowers are very different.  This was a first-time observation for me.

photo of large flower fairybells

Large flower fairybells


photo of tall redwood trees

Tall redwood trees






As I took a break sitting on a commemorative bench I decided to experiment with taking vertical panoramas of the amazing redwoods.  This is an attempt to convey the majesty of these trees, while being aware that they are only slightly over 100 years old.






Along both Purisima Creek Trail and Craig Britton Trail I encountered quite a few fetid adder’s tongue (Scoliopus bigelovii).  In fact, I saw most stages of the annual cycle, from early leaves to flowers to post-flower seed pods.  This individual, obviously in the flowering stage, was at the lower end of Grabtown Gulch Trail at the junction with Purisima Creek Trail.


photo of fetid adder’s tongue

Fetid adder’s tongue

In other places along my hike I saw periwinkle (Vinca major) as well as remnants of last year’s self-heal (Prunella vulgaris).  When I got to Grabtown Gulch Trail I hiked all the way up it, about 2.3 miles, to the trailhead on Tunitas Creek Rd.  The climb is steady and was the steepest of the day, though it may have seemed a little steeper than it really was because it was at the end of the hike.  As I approached the trailhead I caught a glimpse of brightness through the trees and realized that it was the Pacific Ocean with some reflected late-afternoon sunlight.

photo of Pacific Ocean

Pacific Ocean

This was a wonderful springtime wildflower walk in which I found several flowers that thrive in moist and shady conditions.  It was a delightful variation on my more usual spring wildflower hikes on open grassland hills and ridges.

This entry was posted in Midpeninsula Regional Open Space District, Peninsula, San Mateo County, wildflower hikes and tagged , , , . Bookmark the permalink.

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