By Tom Oberbauer, Past President CNPS-San Diego
San Diego County has varied topography throughout: beaches, mesas and canyons, foothills, mountains, and desert. That makes it somewhat distinctive from other counties that mostly consist of mountain ranges and valleys, like Riverside Co., Los Angeles Co., and parts of Orange Co. Also, the development patterns here have allowed for the persistence of native vegetation on slopes around Mission Valley, along I-5 north of Mission Bay, and along I-8, as well as SR-67 and SR-52.
Because we have such varied topography, we also have a variety of vegetation communities; the patterns and texture of the vegetation are strikingly different depending on where you are. Following adequate rainfall seasons, the vegetation may appear quite vigorous with new growth that fills in gaps created by long, dry summers and falls.
One of the most distinctive vegetation communities in terms of color, texture and patterns is pure Coastal Sage Scrub, Diegan Coastal Sage Scrub: Artemisia californica, Eriogonum fasciculatum, and Rhus integrifolia vegetation.
During dry periods, this vegetation loses many of its leaves.Artemisia californica (California Sagebrush) becomes gray-brown due to shriveled up leaves, and Eriogonum fasciculatum (California buckwheat) may have reddish leaves. Rhus integrifolia (Lemonade Berry) remains green all year. Often a part of Coastal Sage Scrub, Salvia mellifera ( Black Sage), with its drought deciduous leaves, may appear gray and dead when the weather is extremely dry.
However, following good rains, Artemisia californica comes alive as a soft, gray-green color. Morning light brings out the color in patches. This color mixes with the occasional contrasting darker color of Laurel sumac (Malosma laurina). It has a bumpy texture as a result and sometimes the Laurel sumac is partially covered with the bright green vines of Marah macrocarpa (Wild Cucumber) and is mixed with bright green, shiny leaved Toxicodendron diversifolia (Poison Oak). This vegetation is usually on south and west facing slopes, but near the coast it can be on northern slopes. The gray-green color of A. californica is especially striking since none of the other vegetation around is that color.
Along the direct coast, such as Point Loma and around the lagoons in the northern part of the County along I-5, the Coastal Sage Scrub has a dull green color that turns gray-brown in summer, but vegetation with Encelia californica (California Encelia) provides yellow flowered shrubs for a few weeks in early spring. When flowering en masse, the slopes appear with a rough texture yellow color.
On slopes a bit further inland, another shrub that has a dull green color in spring and turns brown in summer is Bahiopsis laciniata (San Diego Sunflower). Bahiopsis laciniata has bright yellow flowers with yellow centers. It grows on south facing slopes along I-15 through Murphy Canyon. Prior to the 1980s, it also covered the south slope along I-8, west of Adobe Falls, near the College Avenue off ramp. However, since then, Cenchrus setacea (Fountain grass) spread into the Bahiopsis laciniata gradually taking it over and replacing it, even in the absence of fire or other disturbances. Only patches of Bahiopsis laciniata remain where once the entire slope was covered with it.
Fortunately, it still covers slopes around Otay Mountain in a variety of locations and into Dehesa Valley and Harbison Canyon.
Chamise (Adenostoma fasciculatum) Chaparral is one of the smoothest, most uniform vegetation communities when viewed from a distance. In the center of the County, Viejas Mountain, Poser Mountain, and even the mesa tops on Marine Corps Air Station Miramar support this vegetation. Where it grows on gabbro and other smooth rock types, including cobblestone formations on eastern Miramar, it has a smooth pattern of dark green with a brown and black base that makes it very dark in appearance. However, in the interior or areas where it is adjacent to Mixed Chaparral, there may be spring time colorations of white from Ceanothus perplexans (Cup-leaf Lilac), a shrub with a warm, creamy scent while in flower.
On north facing slopes in urban San Diego and many of the slopes east of Encinitas and south of Escondido, the vegetation is a mixed chaparral type. In Mission Valley, it has a dark, lumpy appearance due to the variety of plants growing there, one of which is Ceanothus verrucosus (Wart-stemmed Ceanothus), which generates white coloring from tiny flowers in early spring and late winter.
As one travels east toward Ramona or even toward Lakeside, through Mission Trails Park, the Mixed Chaparral takes on a different spring coloration, a darker blue, resulting from Ceanothus tomentosus (Ramona Lilac) and Ceanothus leucodermis (Chaparral Whitethorn) flowers in the millions on the shrubs. After a good rainfall season, the hills may seem deep blue due to these shrubs.
Mixed Chaparral in the back country is more varied. Shrubs of Quercus acutidens (Torrey’s Scrub Oak) grow in rounded ball shapes extending a bit higher than the adjacent chamise and other shrubs, giving Mixed Chaparral a bumpy, uneven texture. When Arctostaphylos (Manzanita) is present, either Arctostaphylos glandulosa (Eastwood Manzanita; below) or Arctostaphylos glauca (Bigberry Manzanita), the shrubs are usually a bit lighter shade of green than the rest of the Mixed Chaparral. They are distinctive and identifiable from a distance.
Colors of Mixed Chaparral in the interior may also be enhanced by blues and whites with Ceanothus leucodermis blues and sometimes pale blues and Ceanothus perplexans, the whites.
The southern part of the County supports a varied and complex pattern of Mixed Chaparral. In the Japatul area, vigorous Mixed Chaparral combines the Ceanothus and Arctostaphylos with the Scrub Oak and Chamise to create a strong and tall growing chaparral. Along I-8, near the turnoff for the Sunrise Highway, Adenostoma sparsifolium (Red Shanks) is dominant and creates a texture that is more fluffy and soft appearing than other Mixed Chaparral, and the color is a little lighter green with some yellow and brown background. In these southern areas, a number of valleys and mesas exist where the chaparral grows down to the edge of the valley or other flatter terrain, and the silver leaved Artemisia tridentata (Great Basin sagebrush) fills in the lower areas. The contrast in color between the chaparral and the sagebrush is striking.
On a number of mountains and peaks with unique soils, especially soils derived from gabbro and metavolcanic rock, a specialized vegetation, with a brilliant green color in spring, has evolved. Chamabatia australis (Southern Mountain Misery; above) has strongly aromatic fernlike leaves and white rose-like flowers in spring. However, the vegetation on north slopes creates a smooth, fresh green color where it grows. At other locations, Hesperocyparis forbesii (Tecate Cypress) and Hesperocyparis stephensonii (Cuyamaca Cypress) grow on the gabbro and metavolcanic soils with a very dark green color of an aery vegetation with bristle-like texture depending on how long since the last fire.
Of course, where a drainage flows through a valley or the soil is deep enough and precipitation great enough, the pattern of chaparral touching a line or patch of Quercus agrifolia (Coast Live Oak), creates a visual design that portrays the diversity and variability of the vegetation contrasts.
Farther east in the desert, the pattern of the vegetation becomes overshadowed by the dryness. With 6 inches of rainfall or less each season, the rocky slopes behind the vegetation become more prominent than the vegetation itself. However, in the chaparral transition zones and juniper woodland areas, the vegetation may create a pattern depending on the slope aspect with the north slopes more heavily vegetated than the south slopes. Junipers can grow as small trees or large shrubs in those areas.
In the mountainous regions of the County, forest vegetation creates its own patterns depending on the mix of trees and shrubs. A remnant stand of old growth forest on Cuyamaca Peak still supports a mix of Sugar Pines (Pinus lambertiana), Incense Cedar (Calocedrus decurrans), White Fir (Abies concolor) and Black Oak (Quercus kellogii).
The taller trees, the sugar pines and white firs, reach a little higher than the other trees in that area. The forests there create more of a 3-D situation in which you are inside it rather than viewing it from afar. However, on Mount Laguna and other parts of our mountains, pine forests composed mostly of Pinus jeffreyi (Jeffrey Pine), create an extensive cover over a large area and when viewed from a hilltop, they create a bristly texture. The view across Mendenhall Valley on Palomar Mountain from the road to the observatory presents a forest of deciduous and evergreen oaks, as well as Jeffrey pines and white firs, a full, rich texture of trees.
Finally, while not so apparent from the ground level, the riparian systems create a cover of vegetation that is also forested and three dimensional. If one ever has the privilege of viewing the Tijuana River Valley from the hills on its south, though its trees are being impacted by shot hole borers, one could see the bright green color and soft texture of the riparian woodlands. The Santa Margarita River near the Camp Pendleton MCAS Airport, and the Sweetwater River upstream from the Sweetwater Reservoir, are other locations of such full cover riparian vegetation.
Next time you are driving around the County, particularly in the spring, look at the hillsides, even those in the City of San Diego, and think about the diverse factors that have created these areas of vegetation and their colors, patterns and textures that exist and even change during the year.
All photos by Tom Oberbauer