Finding Nemo the rare Mount Diablo manzanita

I seem to have a thing for plants that start with A: Aloe, Agave, Acacia, and now Arctostaphylos aka manzanitas. With smooth or peeling bark ranging in color from cinnamon to chocolate, contorted branches, stiff leaves in hues from apple green to silver, and masses of small bell-shaped flowers in late winter frequently followed by tiny fruit resembling little apples (hence the Spanish name), their presence cannot be denied.

While some manzanita species are present in other western states as well—the prostrate kinnikinnick or bearberry (Arctostaphylos uva-ursi) is even found in the polar regions of North America, Asia and Europe—the biggest concentration is in the California Floristic Province (CFP) which stretches from southwestern Oregon into northern Baja California. According to the Field Guide to Manzanitas, 104 of 105 currently recognized Arctostaphylos taxa (species and subspecies) are native to the CFP. (The 105th, oddly enough, grows only at the top of several volcanic craters in Guatemala, thousands of miles from its closest manzanita neighbor.)

The county where I live, Yolo, is home to only one species (the common manzanita, Arctostaphylos manzanita subsp. manzanita), but some of the biggest manzanita hotspots are an easy drive away: Sonoma County (17 species and subspecies), the greater Bay Area (27), and Santa Cruz and Monterey Counties (27). It's one thing seeing plants you like in a residential or public garden, but it pales compared to the real deal: seeing them grow in their natural habitat.

Even though I've done some reading and have seen different manzanita species in botanical gardens, my practical skills at identifying them are virtually non-existent. Some species are very distinct, but many others (especially subspecies) are difficult to tell apart. The best clue is location: the native habitat of a manzanita is probably the best criterion in order to narrow down the possibilities.

Softly undulating hills dotted with oak trees are a typical landscape feature in our part of California

With that in mind, I decided my first manzanita outing of the year should be to a spot that only has two species: Black Diamond Mines Regional Preserve near the city of Antioch in the East Bay.

Located just north of Mount Diablo (3,849 ft.), the most prominent peak in the East Bay and visible for dozens of miles around, the Black Diamond Mines Regional Preserve is only one of two places where the rare Mount Diablo manzanita (Arctostaphylos auriculata) is found. The other is Mount Diablo itself, of course. This exclusive restriction to a very narrow geographic area—called "hyperendemism" by the experts—is typical of quite a few manzanitas. In fact, some species are only found on one mountain and nowhere else.

From 1850 to the early 1900s, this area was the largest coalfield in California, hence the moniker "black diamond." At the height of the mining operations, there were three towns, the largest of which had a population of over 1,000. The only thing left now is Rose Hill Cemetery, an easy walk from the Greathouse Visitor Center parking lot. The remains of 12 mines (both coal and sand mines), with over 200 miles of shafts, still exist. They're closed off, but you can look into a few of them through metal fencing. From March to November, there are 90-minute weekend tours of the Hazel-Atlas Mine that produced silica sand for manufacturing bottles and jars.

The site 6,000-acre Black Diamond Mines Regional Preserve has 60 miles of trails. My partner in crime, Ursula, and I took the Chaparral Loop Trail from the Greathouse Visitor Center parking lot. It was recommended by my friend Troy McGregor who goes to Black Diamond regularly—and a great recommendation it was, as you'll see from the 70 (!) photos in this post.

Bare trees in the winter have a beauty all their own

The green stuff is miner's lettuce (Claytonia perfoliata). California Gold Rush miners ate it to prevent scurvy. Apparently it's very high in vitamin C.

It didn't take long before we saw the first manzanita.

It's common manzanita (Arctostaphylos manzanita subsp. manzanita). It's one of the largest species, with the potential to grow to tree-like proportions. The leaves are a shiny green (actually a richer greener than the photo below suggests), and the flowers a pure white.

The next two photos are of the actual trail. As beautiful as it is, I would not rate it as accessible to people with physical disabilities. 

Another Arctostaphylos manzanita subsp. manzanita

Arctostaphylos manzanita subsp. manzanita flowers

The fallen flowers look like snow

Lots of Arctostaphylos manzanita subsp. manzanita, but no sight of Mount Diablo manzanita yet.

  

Arctostaphylos manzanita subsp. manzanita: stunning tapestry of maroon-colored branches, apple-green leaves, and white flowers

This is the trail!

More manzanita snow

Still common manzanita

Big hole in the hillside—tempting...

The ground was soft from the recent rains (as recent as that morning)

View northeast toward the Sacramento–San Joaquin River Delta. The bare rock in the middle is the actual trail.

Finally we came across our first Mount Diablo manzanita (Arctostaphylos auriculata). It's easy to see how different it is from common manzanita.

Common manzanita has leaves which are typically a shiny apple green and stick straight out. Mount Diablo manzanita has leaves which are a dull grayish-green and overlap, clasping the stems. The species name, auriculata, means having two earlike lobes, referring to the deeply lobed leaf bases. 

The flower color can range from almost pure white to a rich pink.

More photos of the scenery and the trail:

In many places, the trail runs over sandstone rock

With no clue to the scale of these images, they could be aerial photos of southern Utah

A younger specimen of Mount Diablo manzanita

The flowers on this specimen were a more pronounced pink

My friend Ursula providing a sense of scale

One living manzanita in a thicket of dead ones. As "drought-tolerant" as they are, the 2011-2017 drought pushed many to the brink—and beyond. 

Flowers a light pink

Flowers almost pure white

Look at the spread of this Mount Diablo manzanita!

Mount Diablo manzanita (Arctostaphylos auriculata) and Coulter pine (Pinus coulteri)

Another large specimen of Arctostaphylos auriculata

Common manzanita (left) and Mount Diablo manzanita (right) growing side by side. I wonder if the two hybridize? I haven't found any references to crosses between these two species.

The next photos are of a particularly pretty stretch along the lower Chaparral Loop Trail:

A tunnel through the manzanitas!

Another spot where the two manzanita species are found side by side

All of these are pure Mount Diablo manzanita

These magenta flowers were another nice surprise. I thought they were a type of Indian paintbrush. Close, but not quite. They're called Indian warrior (Pedicularis densiflora).

Indian warrior (Pedicularis densiflora)

Indian warrior (Pedicularis densiflora)

A wider view:

Filigree of branches:

The trail had been wonderfully scenic from the get-go, and it ended on a high:

Since it was an overcast day, with rain looming almost constantly, we encountered fewer than a dozen people. For long stretches, we had the trail completely to ourselves, with no human sounds other than our voices. Sheer bliss!

Shortly before we reached the final downhill segment that leads back to the parking lot, we saw a good dozen trees covered with this fungus. I'm sure it's a common thing, and it doesn't look like it's doing much harm to the trees. But I must admit that I know next to nothing about tree fungi.

I'm so happy we decided to go on this outing in spite of the threat of rain. While it had rained on and off on the drive from Davis to Antioch, the weather was kind to us during the two hours we were at Black Diamond Mines.

To help you visualize where Black Diamond Mines Regional Preserve is located, here's a handy Google map. San Francisco is in the lower left.

Map data ©2019 Google

The most recent and most complete book on manzanitas is the Field Guide to Manzanitas by Michael Kauffmann, Tom Parker, and Michael Vasey, published in 2015 by Backcountry Press. It covers all 104 taxa found in North America, including Mexico. Useful sections include a detailed description of characteristics; regional keys helping you ID individual species; treatments of each species/subspecies; a list of species found in each California county (sorted alphabetically by county name); a similar list for states other than California; a glossary; and descriptions of manzanita hotspots in seven different areas, including how to get there and which species you will find.

The species treatments use typical botanical terminology, which may be challenging to understand if you don't have some knowledge of botany. For example, the listing for Mount Diablo manzanita (Arctostaphylos auriculata) talks about the leaves being "oblong- to round-ovate" and "canescent," the hairs on the leaves "completely non-glandular," and the fruit "depressed-globose." This may seem unnecessarily jargony, but it's necessary because the differences between two species often come down to small stem, leaf, and fruit characteristics.

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