the Santa Ana Mountains. Horizontal and vertical movements along this fault over the past 5 million years have shifted the Santa Ana Mountains northwest relative to the adjacent landforms to the east, and have raised and tilted the whole mountain block into its characteristic west-sloping orientation. Sudden earth movements along any of these faults have been and will again be responsible for most of Southern California’s devastating earthquakes.
The geologic history of Orange County is a fascinating one, and the diversity of landforms and rocks in Orange County and the Santa Ana Mountains is enough to pique the curiosity of most any amateur geologist. Refer to Appendix 2 for sources of additional information.
Native Gardens
About 800 different kinds of wild flowering plants are found within Orange County’s 782 square miles, a remarkably large number considering its diminutive size among California counties.
There are two reasons for this abundance of plant species. One reason has to do with physical factors: topography, geology, soils, and climate. Countywide, the diversity of physical factors and the complex interrelationships among these factors have led to the existence of many kinds of biological habitats.
The second reason is Orange County’s location between two groups of flora: a southern, drought-tolerant group, most clearly represented by various forms of cacti; and a northern group, represented by moisture-loving plants typical of California’s northern and central Coast Ranges. As the climate changed, varying from cool and wet to warm and dry over the past million years or so, species from one group and then the other invaded the county. Once established, many of these species persisted in protected niches even as the climate turned unfavorable for them. Some survived unchanged; others evolved into unique forms. Some are present only in very specific habitats.
The bulk of Orange County’s undeveloped land can be grouped into three general classes, which botanists often call plant communities or plant associations. In a broader sense, they are biological communities because they include animals as well as plants. These plant communities are briefly described below.
The sage scrub (or coastal sage scrub) community lies mostly below 2,000 feet in elevation and extends east from the coastline to the foothills and lower spurs of the Santa Ana Mountains. The dominant species are small shrubs, typically California sagebrush, black sage, white sage, and wild buckwheat. Two larger shrubs often found here are laurel sumac and lemonade berry, which like poison oak are members of the sumac family. Interspersed among the somewhat loosely distributed shrubs is a variety of grasses and wildflowers, green and colorful during the rainy season but dry and withered during the summer and early-fall drought.
The chaparral community is commonly found above 2,000 feet in the Santa Ana Mountains, where it cloaks the slopes like a thick-pile carpet. The dominant plants are chamise, scrub oak, manzanita, mountain mahogany, toyon, and various forms of ceanothus (“wild lilac”). These are tough, intricately branched shrubs with deep root systems that ensure their survival during the long, hot summers. Chaparral is sometimes referred to as an “elfin forest,” a literal description of a mature stand. Without the benefit of a trail, travel through mature chaparral, which is typically 10–15 feet high, is almost impossible. Sage scrub and chaparral vegetation tend to intermix readily throughout the Santa Anas, the chaparral preferring shadier, north-facing slopes, and the sage scrub preferring hot, dry, south-facing slopes.
The southern oak woodland community is found in scattered locations throughout the county, from the bigger coastal canyons in the San Joaquin Hills to moist flats and canyons throughout the Santa Ana Mountains. Within the Orange County area, the indicator tree is the live oak, but sycamores may also be abundant. In the Chino Hills, native walnut trees form a major component of the southern oak woodland community. Beneath the trees, various chaparral and sage scrub plants often form a sparse understory.
Aside from these three widespread natural communities, much of the nonurbanized land in and around Orange County is given over to agriculture and grazing. Areas characterized by heavy grazing have grassy flats and bald slopes called potreros (pastures) supporting mostly nonnative grasses and herbs, such as wild oats, filaree, mustard, and fennel.
To a small extent, several other natural communities are found in Orange County: rocky shore, coastal strand, coastal salt marsh, freshwater marsh, riparian woodland, and coniferous forest.
The riparian (streamside) woodland community, existing in discontinuous strips along some of the bigger watercourses, is perhaps the most biologically valuable. Not only is this kind of environment essential for the continued survival of many kinds of birds and animals, it is also very appealing to the senses. Massive sycamores, cottonwoods, and live oaks and a screen of water-hugging willows are the hallmarks of the riparian woodland. Most of this habitat has already been usurped by urbanization and the development of water resources.
The coniferous (cone-bearing-tree) forest community was once more widespread in the Santa Ana Mountains. The west-side canyons were logged a century ago in connection with various short-lived mining booms; this logging and subsequent wildfires have reduced the forest to small, isolated patches that cling to the slopes of the deeper canyons. Bigcone Douglas-fir and Coulter pine are the indicator species of coniferous forest in the Santa Anas, although live oaks and other broadleaf trees are also frequently present.
A few species of plants of limited geographic extent in the county are worth noting:
Knobcone pine, somewhat widely distributed in the northern and central California Coast Ranges and the foothills of the Sierra Nevada, clings to a small toehold in the Santa Ana Mountains on the slopes of Pleasants Peak. Here, it finds the warm, dry climate and the particular kind of soil—serpentine—it thrives on.
Bigleaf maple, California bay (bay laurel), and madrone, found in the west-side canyons of the Santa Ana Mountains, are three more examples of trees at or close to the southern end of their natural range. The madrones are restricted to a tiny area in upper Trabuco Canyon.
The Tecate cypress, once widespread throughout Southern California, is now confined to small arboreal islands in San Diego County, in northern Baja California, and along the slopes of Coal and Gypsum Canyons in the northern Santa Anas (just outside the Cleveland National Forest boundary). Here, it finds the extra moisture, in the form of nocturnal fogs moving in from the coast, that it needs in order to hold onto its biological niche.
Late winter to mid-spring is the best time to appreciate the cornucopia of Orange County’s native plants. Many of the showiest species—the annual wildflowers—burgeon at this time, and other plants exhibit fresh, new growth. For more information about the wildflowers, shrubs, trees, and other flora typically found in Orange County, see Appendix 2.
Creatures Great and Small
Your first sighting of an eagle, mountain lion, badger, or any other seldom-seen form of wildlife is always a memorable experience. Because of the diversity of the still-natural parts of Orange County, they are host to a healthy population of indigenous creatures, including a few rare and endangered species. If you’re willing to stretch your legs a bit and spend some time in the areas favored by wild animals, you’ll eventually be rewarded by some kind of close visual contact.
While doing fieldwork for an earlier edition of this book, Jerry Schad was lucky to spot a young mountain lion while hiking in the Santa Ana Mountains, and a golden eagle while driving on Interstate 5 through the hills of south county.
The most numerous large creature in Orange County is the mule deer, with a population of perhaps several hundred. These deer prefer areas of forest and chaparral, especially at higher elevations in the Santa Anas.
The mountain lion, once hunted to near-extinction in California, has made a comeback as a protected species. Perhaps two dozen
