Sometimes the good stuff is hiding in plain sight......

For years I was told to check out Otay Mountain. I resisted. To me, it did not have that impressive stature that would normally lure me to a place. It looked plain and drab and I was clueless about its floristic bounty. I judged it from afar, sadly. Then one day, I decided to give it a try. I read that it had a "few" rare plants that I thought might be nice to see. So I went. 

At the time, many years ago, I was by no means qualified to suss out rare plants. But rare plants or not, Otay Mountain won me over. The views alone were beautiful. And despite being able to suss out any rare plants, I was overjoyed to see so many wonderful and beautiful plants all growing together. There was so much to explore and see. And there was a certain excitement in knowing that so many impressive plants were all tucked within this place that rises from a sprawling suburb.      

Otay Mountain is a landmark for rare plants and most famously known for being home to two of California's most rare plants - Hesperocyparis forbesii (Tecate Cypress) and Fremontodendron mexicanum (Mexican Flannelbush). Otay Mountain also has its own specie of Manzanita (Arctostaphylos otayensis) and Ceanothus (Ceanothus otayensis), both of which are also rare. Apparently, some 20 species of sensitive plants and animals call Otay Mountain home.  

A view of Otay Mountain in eastern San Diego County: Otay Mountain is located in southern San Diego County. It tops out at 3,500' in elevation. On the lower slopes of the mountain is a dense swath of California Buckwheat, Laurel Sumac, Chamise and California Sagebrush. Higher up, the slopes become more precipitous. Rock outcroppings begin to punch through the vegetative cover where select species of Manzanita, Ceanothus, Summer Holly, and Chaparral Pea take root. 


Some Geology

Otay Mountain is part of a larger chain of extinct volcanoes called the Santiago Peak volcanics that date back to the Early Cretaceous (145 - 100.5 Ma). These former volcanoes were the result of a magmatic arc that once ran along the subduction zone between the Farallon and North American Plates. As the Farallon Plate moved eastward and subducted beneath the North American Plate, it melted and molten magma rose to the earth's surface. A chain of volcanoes then formed. The volcanic activity ultimately ceased but the Farallon Plate continued to push them eastward. Eventually the peaks crashed into the North American Plate and were added on as "accreted terrane". 

For a visual explanation, check out these videos:



A map showing some of the Santiago Peak Volcanics within San Diego County

Today, the Santiago Peaks volcanics run from northern Baja to southern Orange County. They run as a patchwork of peaks and ridges that lie several miles inland from the immediate coastline. And what we see today is only a twisted and contorted version of what once existed.

These peaks are more like small pieces of the underbelly to a former volcano. Through eons of time, these pieces have been uplifted, warped and worn back down into a distinct mixing of rock and soil. Fault line activity placed compressive forces on them and pushed them upward into the peaks and ridgelines we see today. 

A dry south facing slope with Toyons, Chaparral Yucca, Ceanothus spp, Summer Holly, & more.

When it comes to rare plants, Otay Mountain has two critical ingredients: rare geology and unique geography. 

Otay Mountain is a mixture of metavolcanic and sedimentary soils. Likewise, the geology of Otay Mountain is not widespread throughout southern California. It exists as a patchwork amidst a more widespread geologic setting, which sets the stage for unique developments. In short, plant speciation and evolution begin to play their hand. And we are left with some beautiful and amazing plants.


Some Plants (rare and not) of Otay Mountain

Chamaebatia australis - Southern Mountain Misery

In California, Southern Mountain Misery is only found on Otay Mountain. It is the sister specie to the more common Chamaebatia foliolosa (Sierran Mountain Misery), which grows throughout the Sierra Nevada. Presumably, an ancestral specie grew throughout California during a time when the climate was wetter. In that case, Southern Mountain Misery would be the descendant specie that evolved under a warmer and drier climate. Monsoonal flows that make their way into southern San Diego County may help this species survive today's warmer and drier climate.  MORE INFO

Hesperocyparis forbesii  - Tecate Cypress

Otay Mountain is home to one of the few stands of Tecate Cypress present in California, with the stand on Otay Mountain being one of the largest. Tecate Cypress is a relic species that was presumably more wide spread during a time when California’s climate was wetter. The hotter and drier climate of California’s present climate means Tecate Cypress has fewer favorable habitats where it can grow. It must now find ecological niches where it can retain enough competitive advantage to persist alongside other hot and dry adapted vegetation. Occurrences of unique or distinct geology has afforded those ecological niches.  

Cypress species are notorious for tolerating nutrient deficient soils. They even tolerate soils saturated in heavy metals. Their ability to tolerate these “poor” soils gives them the competitive advantage they need to persist amongst the greater vegetative community. The metavolcanic and ultramafic geology of Otay Mountain, and that of the Santiago Peak volcanics in general, likely plays a hand in the presence Tecate Cypress. The rock outcroppings atop Otay Mountain include rocks that are high in magnesium and iron. These rocks create the nutrient poor soils that can restrict the recruitment of other more typical shrub species. By virtue of a restrictive soil type, Tecate Cypress finds the competitive advantage it needs to outcompete a broader vegetative matrix.  MORE INFO

Ribes indecorum - White Flowering Current

Ceanothus otayensis - Otay Mountain Ceanothus


Xylococcus bicolor - Mission Manzanita

Mission Manzanita is like a Toyon meets a Manzanita. This is a rare plant that only grows in the maritime chaparral of southern California and northern Baja. Its similarity to Manzanita is due to it being a somewhat close relative within the Ericaceae family. In Spring, white "urn-like" flowers appear. It's a versatile and attractive shrub with great ecological value, but also works well in ornamental settings.  MORE INFO

Arctostaphylos spp. - One I failed to correctly ID  

The floristic bounty of Otay Mountain

This metavolcanic rock outcropping is indicative of all that Otay Mountain offers. In this photo is Southern Mountain Misery (Chamaebatia australis), Otay Manzanita (Arctostaphylos otayensis), Laurel Sumac (Malosma laurina)  and Chaparral Yucca (Hesperoyucca whipplei)...A complete mixing of rare and endemic plants alongside denizens of the southern California chaparral.   

With more to be continued......

And a view across the border into northern Baja. Supposedly, one of (if not the only) occurrences of Ornithostaphylos oppositifolia (Baja Birdbushes) within the state of California lies within this watershed. May it live on in peace.  


Herzig, Charles T., et al. "Santiago Peak volcanics: Early Cretaceous arc volcanism of the western Peninsular Ranges batholith, southern California." Peninsular Ranges Batholith, Baja California and Southern California: Geological Society of America Memoir 211 (2014): 345-363. https://doi.org/10.1130/2014.1211(09)

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