The California geography is as varied as any state in the United States, more so than many countries. The elevation ranges from, the lowest point on the continent, more than 200 feet below sea level, to the highest in the lower 48 states, over 14,000 feet! Temperatures across the state vary from hot southern deserts to frozen alpine glaciers. Average annual rainfall also differs substantially. Anyone who has travelled through even a small part of the state can hardly help but notice that the vegetation changes, sometimes dramatically, from one area to another. The forests of California’s north coast contain the worlds tallest trees, some exceeding 300 feet, while much of the central valley, though rich in plant life, contains hardly any trees at all.
Understanding the area in which you live should be the first step in determining what natives are best included in your landscaping plans. It should not be surprising that the plant communities within each of the various areas is different. In most cases, a few species dominate an area’s ecosystem. The entire community of plants and animals is effected by those dominant species. The relative mixture may change from spot to spot, but the general composition will stay the same throughout the area, gradually giving way to another type of community.
California can be generally divided into ten vegetative zones:
North Coast Forest
California’s coastal grasslands stretch, on and off, all along the Pacific coast from Tijuana to the Oregon border. Though discussed together here, there are wide differences that occur over that distance, best exemplified by average annual rainfall — about 8 inches in San Diego County to over 80 inches in Del Norte County. As one might expect, the type and density of vegetation varies as well.
There are commonalities along the California coast as the entire area’s weather is dominated by the Pacific Ocean. The effect is to greatly modify the climate, providing a relatively uniform temperature throughout the year. Winters are mild and summers are cool in the north to warm in the south. Rain occurs from late fall through the spring with a summer drought. The summer fog provides some critical moisture to the soil and plants. Areas adjacent to the ocean have an almost constant wind, heavily laden with salt.
The plants that dominate the coastal grasslands vary from one community to another. Much of the area is covered by chaparral, containing Manzanita (Arctostaphylos spp.), Sage (Artemisia spp.), Coyote Bush (Baccharis spp.), Oaks (Quercus spp.), Junipers (Juniperus spp.), and so on. The areas dominated by grasses are, in general, much changed since the arrival of the Spanish missions due to the introduction of large numbers of cattle and sheep. The native grasses evolved with grazing animals such as elk and deer, but for a variety of reasons never faced the pressure that the sheer numbers of the domestic stock create. In response to the decline of the native forage, first Spanish, then later American settlers over-seeded with exotic grasses. More recently, agriculture and urban sprawl have taken their toll, and introduced more new contenders. The natives, mostly perennial bunchgrasses, have not done well competing with the introduced annual grasses. The replacement of natives has been so complete that to a large extent the original distribution and mix of species is not known.
The naturalized European annual grasses appear all along the coast. Native species tend to split, some occurring only in the north, others only in the south. The split tends to occur either around Santa Barbara or the Monterey peninsula though this is quite variable. Natives still common along the north coast include Pacific Reedgrass (Calamagrostis nutkaensis), Pacific Hairgrass (Deschampsia holciformis), and California Bentgrass (Agrostis californica). In the south natives include Crested Stipa (Achnatherum coronata), Foothill Needlegrass (Nassella lepida), Nodding Needlegrass (Nassella cernua), Giant Wildrye (Elymus condensatus), and Thingrass (Agrostis diegoensis). Purple Needlegrass (Nassella pulchra), is perhaps the most widespread native grass, extending down most of the coast.
California’s central valley makes up almost a quarter of the state and is one of the richest agricultural areas in the world. The mild climate provides a long growing season and the soil is extremely fertile. The only ingredient lacking is summer water. That is overcome through irrigating with water made available by a system of state and federal dams and aqueduct systems. Today such crops as cotton, rice, grapes, and all manner of vegetables are the dominant species over most of the area.
The central grasslands extend across the flat valley from Redding south to the desert area, just north of Bakersfield, from the Sierra foothills west to the coastal ranges. At its margin, the grasslands merge gracefully into other communities, usually woodland, often with no clear border. The hills east of the San Francisco Bay, for instance, contain grasslands with many scattered, medium-sized oak trees forming a savannah that is part prairie, part forest.
Rain falls during the Autumn, Winter, and early Spring, leaving the rest of the year dry. Rivers flowing from higher elevations bring water through the valley provide an occasional summer oasis. Depressions that catch rainwater, called vernal pools, or “hog wallows”, were once a common feature. These wet spots, typically a few feet deep and up to half a mile across accumulate winter rain then dry out in the summer. A number of plants, primarily annual grasses and wildflowers, evolved in this unusual environment and are restricted to it. As time goes on, these bogs are becoming more rare, being filled for agricultural use or housing.
The temperatures in this area are mild, though with more seasonal fluctuation than the coastal area. Temperatures can exceed 100 degrees in the summer, particularly in the south, and short-lived frosts occur in winter.
Originally the area, referred to as the “Pacific Prairie”, was dominated by perennial grasses and a dazzling display of wildflowers. John Muir provided descriptions during the second half of the last century that are truly amazing. He writes of a sea of color “where your foot would press about a hundred flowers at every step.”
Fire has always played a natural part in maintaining much of the California landscape. In the central valley the effect of fire has been to keep the scattered oaks and annuals to a minimum, allowing the perennial grasses and wildflowers continued dominance. It has been estimated that naturally caused fire swept through most areas of California on an average of every five to ten years. This removed underbrush, often enough to keep the amount of available fuel down, resulting in fires that were relatively cool. The dormant, above ground portions of the perennials would burn well enough, though many contained enough moisture to be somewhat fire resistant, but the root systems normally survived to produce new plants and seeds the following season. Woody plants like oaks, annuals, and most surface seeds did not often survive. Today’s fire control practices, while perhaps necessary, have contributed to altering the flora of the valley and the rest of the west.
As in the rest of California, the composition of the plant communities of the central grasslands depended largely on the amount of water available. Grasses that originally dominated the drier area of both the flat plains and adjoining hills included Purple and Nodding Needlegrass (Nassella pulchra and N. cernua), California and Small-flowered Melic (Melica california and M. imperfecta), California Broome (Bromus carinatus), Blue Wildrye (Elymus glaucus), and others. Deergrass (Muhlenbergia rigens), Creeping Wildrye (Leymus triticoides), Wheatgrass (Agropyron spp.), among others grew in the rich soils along the marshes and rivers. Other species of grasses occurred in more specialized environments such as the vernal pools and marshes.
The common belief is that only a few annual grasses grew in this region, most common in the less fertile, stony soils were the perennials had a more difficult time surviving. A minority point of view is that native annuals were much more important. This theory is based on observations of other areas around the world with similar climates. In those places, long periods of drought seem to favor annual grasses that avoid the dry periods as seeds. The amount and timing of moisture probably had a large impact on the relative mix of annual and perennial grasses, but no one knows for sure.
A diverse variety of wildflowers originally made a spectacular showing in this region. Curly Dock (Rumex crispus), and California Goldenrod (Solidago californica) were common. Yellow flowers included Goldfields (Lasthenia californica), Common Groundsel (Senecio vulgaris), Tidy Tips (Layia platyglossa), and Owlclover (Orthocarpus spp.). White flowers included Common Horehound (Marrubium vulgare) and Milkweed (Asclepias fascicularis). Violet to blue flowers included Baby Blue Eyes (Nemophila menziesii) and Brodiaeas (Brodiaea spp.).
North Coast Forest
The northern coastal forest extends from Monterey north to Alaska along the Pacific Ocean in a band that is narrow in the south, widening through Oregon and Washington, and thinning through British Columbia to Alaska. Ocean air moderates temperatures throughout the year and provides constant moisture. Fog and overcast skies are abundant. The southern part of this region, in California to Oregon and Washington, undergoes the West’s summer drought, decreasing in severity to the north.
As with the other areas, there are various communities within this area. They are all dominated by coniferous trees, often among the largest and most long-lived in the world. The famous Redwood groves of northern California and the Olympic Rain Forests of Western Washington are found here. The Coast Redwood often exceeds a height of 250 feet and occasionally surpasses 300 feet. Douglas Fir (Pseudotsuga menziesii), an important timber tree, sometimes also tops 200 feet. Sitka Spruce (Picea sitchensis), Western Hemlock (Tsuga heterophylla), Noble Fir (Abies procera), and Pacific Silver Fir (A. amabilis) dominate parts of the area, as well.
Much of the California northern coast forest is presided over by Coast Redwoods (Sequoia sempervirens) though some of the most northern inland parts are dominated by Douglas Fir (P. menziesii). Redwood forests occur along the Pacific coast in a band from 5 to 35 miles wide from Monterey north into Oregon. They require constant moisture, taking advantage of relatively abundant rainfall and fog, which can provide as much as twelve addition inches of moisture in the dry summer. In its southern extreme, Redwood forests are restricted to moist bottoms along streams.
Redwoods maintain their supremacy through several interesting strategies. Their unsurpassed height and longevity give them some obvious advantages. Just as important is their tolerance of shade; a small tree can withstand more than 400 years under the closed canopy of its parents, waiting for an opening that, once available, it will quickly fill. Redwoods also have the ability to sprout new growth from its roots, trunk, or stump. They will even sprout a new crown should the old one be destroyed by wind, fire, or lightening. At this writing, the tallest known tree in the world (over 350 feet) is in the process of doing just that! Rapidly closing openings in the canopy prevent foot holds being established by competitors, such as Douglas Fir, that require those openings to survive. Further, should a long term opening occur due to logging, fire, or the demise of old trees, the roots can sprout new shoots in a few weeks, sending them up to seven feet tall in the first year, out growing all of its rivals.
Fire is a constant threat in the west from both man natural causes. Redwoods must withstand these fires many times during their long lives. Thick, fire resistant bark and moist, slow burning wood allow mature Redwoods to weather all but the hottest inferno. Blackened scars, sometimes a century or more in age, attest the giants’ ability to withstand fire.
Redwood forest communities, though often reasonably pure, can include a number of other trees. The community can contain a mixture of conifers and deciduous trees and shrubs, particularly if a break in the over story allows light to penetrate. Douglas Fir (Pseudotsuga menziesii) is one of the most consistent residents north of Mendocino. Western Hemlock (Tsuga heterophylla) and Sitka Spruce (Picea sitchensis) are common north of Eureka, and are scattered to the south. Alders (Alnus spp.) grow along the coast and streams with Willows (Salix spp.) and Bigleaf Maple (Acer macrophyllum). Tanoak (Lithocarpus densiflorus) and Pacific Madrone (Arbutus menziesii) can be found in the drier, more open forests. These trees all require some break in the canopy allowing them at least minimal light.
The lower layers are made up a variety of shrubs such as Vine Maple (Acer circinatum), Hazelnut (Corylus cornuta californica), and Oregon Grape (Berberis aquifolium); ferns, Sword Fern (Polystichum munitum) being the most common; and, infrequent wildflowers like Trillium (Trillium ovatum) and Red Violet (Viola sempervirens). Redwood Sorrel (Oxalis oregana) is a common ground cover.
Redwoods love the seaside moisture but cannot tolerate the harsh winds and salt spray at the very edge of the water. For these reasons, they leave the ocean border to others. In the far northern part of the California coast and beyond, Sitka Spruce, Western Hemlock, and Grand Fir (Abies grandis) fill the gap. Most of California’s Pacific rim forest is made up of pines, even well south of the Redwood’s range. The most common of the pines is the Bishop Pine (Pinus muricata), which does well on exposed headlands and poorly drained soil. Monterey Pine (P. radiata) occurs in an extremely limited range within this belt. Shore Pine (P. contorta) and Monterey Cypress (Cupressus macrocarpa) also grow in limited areas. Many of the trees in the most exposed areas suffer dwarfing and other deformities. Although Big Sur and the Monterey peninsula are famous for such trees, they are present all along the seaboard.
At the edge of the California grasslands, where it meets the coastal and mountain forests is an area known as woodlands. This area encloses the central valley, occurs around the San Francisco Bay, and also extends south into the Baja peninsula. Woodlands are areas that contain elements of both the forest and grasslands. It is generally much more open than a forest and the trees tend to be different and much smaller. Grasses and wildflowers are abundant below and between the trees, but again, they are somewhat different and less dense than in the true grasslands.
It is interesting to note that this type of setting is the most widely desired by man. Perhaps because we evolved in the woodlands of East Africa, we often try to replicate this setting by clearing places in forests or planting trees and bushes in open places; the objective is the mixture of sun and shade found in woodlands.
Woodlands occur naturally as a result of a relatively unique and narrow climate. Abnormal conditions, such as fire, can allow a woodland to develop as an temporary phenomenon. However, in order for a woodland to be a permanent feature, or climax community, the area must have a moderate temperature and enough water to support drought resistant trees, but not enough to allow a forest to dominate. These conditions are rare on a global scale, and so are woodlands.
The dominant tree in California’s woodlands varies based on temperature and the available water. The western hills that sit between the damp coastal forests and central grasslands from San Francisco south tend to support primarily evergreen oaks. Deciduous oaks, particularly Blue Oak (Quercus douglasii), are more common on the cooler inland foothills east of the central valley. Certainly there is much variety within these generalizations; they merely refer to relative abundance. Both evergreen and deciduous oaks grow throughout along with California-laurel (Umbellularia californica). Digger pine (Pinus sabiniana) grows in the moister portions of foothills, while California Black Walnut (Juglans californica) is found in the south and Pacific Madrone (Arbutus menziesii) is common on the coastal hillsides. Along the margins where the woodlands merge with forests, the mingling of species can be rich.
There are four species of evergreen and four deciduous oaks that occur commonly in the California woodland areas. The evergreens are: Coast Live Oak (Quercus agrifolia) near the coast, Engelmann Oak (Q. engelmannii) south of Los Angeles, Interior Live Oak (Q. wislizenii), and Canyon Live Oak (Q. chrysolepis) throughout. The deciduous oaks include Oregon White Oak (Q. garryana) north of San Francisco, Valley Oak (Q. lobata) on both sides of the central grasslands, California Black Oak (Q. kelloggii) throughout, and Blue Oak (Q. douglasii) surrounding the central valley.
A number of shrubs grow with and beneath the oaks. They include Redberry and California Buckthorn (Rhamnus crocea & R. californica), Manzanita (Arctostaphylos spp.), California Buckeye (Aesculus californica) in the north, and Sumacs (Rhus spp.) in the south. Poison Oak (Toxicodendron diversilobum) and California Wild Grape (Vitis californica) also grow here.
The native perennial grasses that originally covered the ground within the woodlands have undergone the same assault as elsewhere: wholesale replacement by exotic annuals. Native grass stands are nearly non-existent in the coastal areas. In the Sierra foothills, they still survive in greatly reduced stands. The native species that apparently were once common are similar to those of the central grasslands, Needlegrasses, Melics, Broome, etc., along with Bluegrasses.
There are several river systems that run through California, carrying snow melt from the Sierras and draining seasonal rainfall. These rivers and the streams that feed them form a rare community in the California landscape, both in terms of their relative lushness and the variety of plants found there. The most unique feature of the riparian ecosystem is the constant availability of water. The plants that live along the waterways and around freshwater marshes do not have to deal with California’s seasonal drought, and therefore do not normally occur in the other communities. The lack of moisture stress allows the area to support one of the most varied combinations of plant life in the state. It is, however a small community, often restricted to a narrow band only a few yards wide.
The trees that grow along California rivers and streams forming the canopy include Black and Fremont Cottonwoods (Populus balsamifera trichocarpa and P. fremontii), Red and White Alder (Alnus rubra and A. rhombifolia), Oregon Ash, (Fraxinus latifolia), California Sycamore (Platanus racemosa), and Box Elder (Acer negundo). Oregon White Oak (Quercus garryana) and California-laurel (Umbellularia californica) grow here as well as elsewhere. Several varieties of Willow (Salix spp.) grow in the damp parts of California. A few of the Willows can get up to 50 feet in height, but they are normally shrub sized, under 20 feet. The brush along these streams, whether under a canopy of trees or alone, is often quite thick, including a number of vines like California Wild Grape (Vitis californica), shrubs include Poison Oak (Toxicodendron diversilobum), Viburnum (Viburnum edule), California Rose (Rosa californica), Buckthorn (Rhamnus spp.), Raspberries (Rubus spp.) and others.
Smaller herbs, wild flowers, and grasses often must compete with the taller woody plants for sunlight and so are normally either shade loving, like the ferns and Horsetail (Equisetum spp.). Creeping Snowberry (Symphoricarpos albus) and Nettles (Urtica gracilis) are common. Deergrass (Muhlenbergia rigens), Creeping Wildrye (Elymus triticoides), Wheatgrass (Agropyron spp.), are among the grasses that grow here. Cattail (Typha spp.) and Tule (Scirpus spp.) grow in still water along the edge of streams and in marshes.
Areas dominated by woody brush, often bordered by forest or woodland, are know as chaparral. These can be large areas and as a climax community normally occur on well drained slopes too dry to allow the larger trees. There are quite a number of types of chaparral within California, each growing in different areas under different conditions. The dominant shrubs tend to be woody broadleaf evergreens that have several strategies to deal with drought. Some of the dominant species are Ceanothus in Northern California, Manzanita (Arctostaphylos spp.) in high elevations often with Mountain Mahogany (Cercocarpus betuloides) in the foothills, Scrub Oaks (Quercus dumosa and Q. berberidifolia) and California Fremontia (Fremontodendron californica) in wetter areas, and Chamise, sometimes called Greasewood (Adenostoma fasciculatum), in the south.
There is also a wetter community very similar to chaparral, called “scrub” which is also made up of shrubs. Along the north coast, in the fog belt, it contains combinations of Coyote Bush (Baccharis spp.), Sticky Monkeyflower (Mimulus aurantiacus), and one of several woody Lupines (Lupinus spp.) as well as several others. Sage scrub is found on hills along the coast from San Francisco south. It includes several types of Sage (Artemisia spp.) and Buckwheat (Eriogonum spp.). Herbaceous plants and wildflowers that occasionally make an appearance include Woolly Blue Curls (Trichostema lanatum) in dry areas, Painted Cup (Castilleja foliolosa) and Cow Parsnip (Heracleum lanatum) in the north, and Golden Yarrow (Eriophyllum confertiflorum), and California Encelia (Encelia californica) in the south.
Thick, pure stands of Manzanita or Chamise tend to force out all other types of plants. Where the chaparral or scrub is mixed, grasses frequently establish themselves. There is some evidence that, particularly in the south, grassland is slowly overtaking the less dense areas. Crested Needlegrass (Achnatherum coronata) and Foothill Needlegrass (Nassella lepida) are common in the south, California Stipa (Achnatherum occidentalis californica) and Melics in the north. Woodland grasses can also often be found here.
Fire is important to all of the chaparral and scrub communities, in some cases being the reason they exist. The denser, woody stands need fire to remove the old dead debris to make room for new growth and to return the nutrients tied up in them to the soil. Often, following a fire, the existing plants will send up new shoots from the surviving root system. In other cases fire prepares the area for seedlings that would otherwise not germinate. For a few years, until the brush re-establishes its dominance, a variety of annuals can make an appearance.
The montane forests occur between about 1500 and 6500 feet in both the Pacific Coast Ranges, between 2000 and 6000 feet in the northern Sierras to a range of 5000 to 9000 feet in the southern Sierras as well as a few sites in Southern California to Baja. As a general rule, in California annual precipitation increases with altitude and latitude. The average temperature decrease over the same range. The montane forest, dominated by conifers, begins where rainfall reaches around 25 inches a year and extends through the mid-elevations.
This community receives more moisture than most of the state, up to 80 inches in the higher elevations, but almost none of it falls in the summer. Plants that grow here must still have some strategy for surviving the seasonal drought. Although the winter temperatures are substantially lower than most of California, they are quite mild compared to most conifer forests in other mountains around the world. Freezing temperatures on winter nights are common throughout the area, but temperatures below zero are quite rare.
There are a number of forest types within the Montane Forest area, each with its own blend of plant types. The dominant species throughout are conifers, normally occurring in combination, though occasionally in pure stands. Ponderosa Pine (Pinus ponderosa), Douglas Fir (Pseudotsuga menziesii), and White Fir (Abies concolor) combinations are dominant in large areas all through this community. Ponderosa Pine is most common in the lower elevations and on the hotter, drier slopes. The two firs are more numerous in the higher, cooler areas. Other trees mingle with these in varying numbers depending on the local conditions. Perhaps the most famous of these is the Giant Sequoia (Sequoiadendron giganteum), which occurs in cool areas where the soil contains moisture throughout the year. California Black Oak (Q. kelloggii) is a fairly common member of this group as is Incense-cedar (Calocedrus decurrens).
Jeffrey Pine (Pinus jeffreyi) is found across this community becoming dominant, sometimes in pure stands, in high elevations, on serpentine soil, and in colder areas. Jeffrey Pine is tolerant of such a wide range of conditions that it occurs over the length of California and, in varying numbers, in most of the forest communities above 4,000 feet. California Red Fir (Abies magnifica) becomes dominant at the higher elevations of this community in the Sierras, occurring well into the subalpine region. A variety of this tree, Shasta Red Fir (A. magnifica shastensis) fills the same niche in the North Coast Range. Some Red Fir stands in the Sierras are very dense and almost pure. Otherwise Red Firs mix with White Fir in the lower part of its range, Mountain Hemlock (Tsuga mertensiana) and Lodgepole Pine (P. contorta murrayana) at the higher end, and Jeffrey Pine and Incense-cedar throughout.
The Firs and Pines throughout this region often exceed a height of a hundred feet. They can form a dense canopy, but often do not, allowing other, smaller trees and shrubs to form lower layers. Pacific Dogwood (Cornus nuttalli), California-laurel (Umbellularia californica), White Alder (Alnus rhombifolia), Bigleaf Maple (Acer macrophyllum), and Pacific Madrone (Arbutus menziesii) grow in the lower areas. Red Huckleberry (Vaccinium parvifolium), California Hazelnut (Corylus cornuta), Thimbleberry (Rubus parviflorus) and others often form the shrub layer. Manzanitas, particularly Greenleaf Manzanita (Arctostaphylos patula), and any of several types of Ceanothus are the most common shrubs in the driest areas of all elevations, growing under the trees or forming an intermittent chaparral. Mountain Mahogany (Cercocarpus betuloides), Sage (Artemisia spp.), and Scrub Oaks (Quercus dumosa and Q. berberidifolia) sometimes join in the underbrush.
At ground level, quite a number of wildflowers and several grasses can be found where enough light penetrates to allow them. Evening Primrose (Camissonia spp.), Pussypaws (Calyptridium umbellatum), Western Peony (Paeonia brownii), and Larkspurs (Delphinium spp.) grow on open, dry ground. Mountain Pennyroyal (Monardella spp.), White-flowered Hawkweed (Hieracium albiflorum), and Goldenaster (Heterotheca spp.) grow on higher, moist sites. The native grasses that once grew in mountain meadows and throughout this area have suffered over grazing and the introduction of exotics, as elsewhere, but have probably fared at least a little better here. This may be due to the harsher environment, and also that it is somewhat less accessible than the lower and more coastal areas. There is quite a variety of native grasses that grow in parts of this area. Broomes, Melic, Hairgrass, Fescues, and Bluegrass all have several species represented here.
The area above the montane forest, up to the treeline is known as the “Subalpine” zone. The down-slope margin is not a clear division, rather an area of gradual decrease in the relative number of Firs and other mid-elevation species in favor of the more winter hardy high-elevation trees. The upslope treeline is also a transition area, though usually a narrower one, where the forest yields to clumps of trees that may dwarfed and deformed. The only real subalpine regions in California are in the Sierra Nevada range between about 7,500 to 9,500 feet in the north to between about 9,500 and 12,000 feet in the south. Subalpine species can be found in the North Coast range, but their occurrence is spotty and in combination with mid-altitude trees.
As a general rule, the most predominant trees in this region are Mountain Hemlock (Tsuga mertensiana) and Lodgepole Pine (Pinus contorta murrayana) in the lower parts, and Whitebark Pine (Pinus albicaulis) in the higher places. Foxtail Pine (Pinus balfouriana) is common up to the treeline in the far southern Sierras. Western White Pine (Pinus monticola), Limber Pine (Pinus flexilis), Red Fir (Abies magnifica), Western Juniper (Juniperus occidentalis), and Bristlecone Pine (Pinus aristata), the longest lived tree in the world, are often intermixed in varying numbers.
The brush level in the subalpine area is somewhat limited by the temperatures, when compared to most of the lower communities. Blue Elderberry (Sambucus caerulea), Red and White Mountain-heather (Phyllodoce empetriformis and Cassiope mertensiana), Alpine Laurel (Kalmia microphylloa), and Wax Current (Ribes cereum) are among those that fill this layer.
Meadows are a common feature throughout the high Sierras in valleys basins. They range in size from hundreds of square feet to hundreds of acres. Though dry in mid to late summer, water is plentiful in the spring from snow melt and glacial runoff. Seasonal marsh-like conditions and periodic fires keep the forest at bay. The dominant resident of these open areas are grasses and sedges. Several species of grass are limited to this region.
The true alpine areas stretch from the tree line to the tops of the highest peaks. The tree line occurs at about 10,500 feet in Yosemite, a little higher to the south and lower to the north. The area varies from the dwarfed plant cover at the tree line to talus slopes and bare rock to places continuously covered by snow and ice. Nowhere are specific micro-climates more important. Conditions that allow one or more plants to sustain themselves may change drastically within a few feet. A single rock or boulder may provide enough shelter for a shrub to grow in its lee.
Moisture and temperature conditions vary here, similar to other California areas. The north is wetter, getting some Summer rain and heavy snow during the very cold Winter. In the South the milder Winter snow depth varies from one year to the next and little rain falls in the Summer. The eastern slopes of the southern Sierras tend to receive only a light Winter snow cover and little rain during the hot Summer.
The Winter snow cover has a major impact on the amount of available moisture in the form of Spring and Summer melt water. It also affords protection from the severe temperatures and strong, drying winds. Regions that are free of snow during the winter do not have the protective cover or a source of Summer moisture often have little, if any, plant life. Conversely, zones with heavy snows are often wet all year supporting meadows, bogs, and marshy places that are abundant with vegetation such as Sedges (Carex spp.), Alpine Willow (Salix anglorum), Alpine Shooting Star (Dodecatheon alpinum), Lemmon Paint Brush (Castilleja lemmonii), Alpine Yarrow (Achillea millefolium lanulosa), Western Needlegrass (Achnatherum occidentalis), and others. The exception, of course, are those places where the snow remains to long to allow an adequate growing season.
The plants found above the tree line are mostly low herbaceous perennials. Some of them are circumpolar, that is, they are found in alpine zones around the north polar cap across North America, Asia, and Europe. Alpine Sorrel (Oxyria digyna) and Roseroot (Sedum rosea) are in this category. Many others have close relatives around the pole.
Since much of the alpine region was recently glaciated, soil is another limiting factor. Bare rock is a common feature, particularly in unprotected places. Thin soil is also common; however, even otherwise denuded spots may accumulate soil in crevices and between rocks that can support Sedges (Carex spp.), Rushes (Juncus spp.), Brewer’s Lupine (Lupinus breweri), Nuttall’s Sandwort (Arenaria nuttallii), and Dwarf Alpine Paintbrush (Castilleja nana). Thin, gravelly coverings support Pussy Paws (Calyptridium umbellatum) and Dwarf Knotweed (Polygonum minimum).
The deserts that occur in the western United States fall within the rainshadow of either the Coastal Ranges or the Sierra/Cascade mountain chain. This is largely because as damp air moves over these mountains, it cools, losing its ability to hold moisture. Rain develops, removing water from the air, one reason why the higher elevations of these mountains tend to be wetter than the adjacent valleys. As the air moves down the leeward slopes, it warms, increasing its ability to carry moisture, but it cannot replace the moisture already lost, so becomes very dry. In fact, this dry air soaks up any available moisture from the land, contributing to the arid conditions. Also, humid air acts as an insulator, moderating both day and night temperatures. Without this protection, desert temperatures tend to sore during the day and plummet at night, both extremes exceeding more humid areas, adding to the hostility of the desert environment.
California deserts can be thought of as three different types based on altitude and location. The first would be the high desert, or California’s portion of the Great Basin that lies east of the Sierras above 4,000 feet. The middle desert would be the Mojave that goes from below sea level in Death Valley to about 4,500 feet. Finally, adjacent to the Mojave and to its south lies the Colorado Desert, California’s portion of the Sonoran Desert, that ranges from sea level to about 2,000 feet.
As in the rest of California, the average rainfall increases with altitude and latitude, while average temperature drops. The Mojave gets from 4 to 15 inches of rain a year and Summer daytime highs of 100° are common as are winter frosts. The Colorado, on the other hand, receives only about 1 to 5 inches of rain and temperatures are somewhat higher, frosts occur only from about January 1st to the middle of February and the Summer daytime highs can exceed 110°.
The Great Basin, though a desert, is quite cold for much of the year. Temperatures drop well below freezing, occasionally to zero in some places. The average rainfall is about the same as the Mojave to a bit more. The topography of the area is complex, containing a series of parallel ridges that rise 3,000 to 4,000 feet above the basin floor. The plant community is more uniform than one would expect due to a fairly constant climate.
The dominant plant over much of the Great Basin is unquestionably sagebrush, probably the West’s most widespread plant. There are many closely related sagebrushes that have been split into several species and a number of varieties. Artemisia tridentata, commonly known as Great Basin Sagebrush (or Big, Basin, or Common Sagebrush), is probably the most prevalent as it is tolerant of a variety of conditions.
Other shrubs that occur with the sages include Rabbitbrush (Chrysothamnus nauseosus), Blackbrush (Coleogyne ramosissima), Mormon Tea (Ephedra spp.), Buffaloberry (Shepherdia argentea), Curl-Leaf Mountain Mahogany (Cercocarpus ledifolius), Gooseberry (Ribes spp.), and others. Wildflowers such as Lupine (Lupinus spp.), Buckwheat (Eriogonum spp.), Monkeyflower (Mimulus spp.), Paintbrush (Castilleja chromosa), Blazing Star (Mentzelia spp.), and Locoweed (Astragalus spp.) can be found between the shrubs. A number of annual and perennial grasses such as Basin Wildrye (Elymus cinereus), Desert Needlegrass (Achnatherum speciosa), and several Bluegrasses (Poa spp.) can also be found.
Pinon-Juniper woodlands occur on slopes where the temperatures are moderate enough and moisture adequate for them. Singleleaf Pinon (Pinus monophylla) prefers the higher slopes blending with Utah or California Juniper (Juniperus osteosperma & J. californica) then fading out to allow pure Juniper stands at lower elevations.
At lower altitudes, where the temperatures increase and annual rainfall drops below seven inches, the Sagebrush relinquishes its reign to members of the Atriplex genus: Shadscale (A. confertifolia), Lensscale (A. lentiformis), and Wingscale (A. canescens). The resulting community is called “shadscale scrub”. These shrubs, sometimes called saltbush, space themselves widely due to the root competition for moisture. Other plants associated with this community include the Spiny Boxthorn (Lycium spp.), Cotton Thorn (Tetradymia spinosa), Bud-Sage (Artemisia spinescens), and several cacti.
The Mojave contains plant communities of several other areas including Great Basin Sagebrush (Artemisia tridentata) with its associates, shadscale scrub, and even Valley Oaks (Quercus lobata), make spotty appearances. This is also true of the Colorado Desert, although to a lesser extent. The most ubiquitous plant in both lower deserts is Creosote Bush (Larrea tridentata) which dominates a majority of the area. Sweetbush (Bebbia juncea), Pygmy Cedar (Peucephyllum schottii), Cheese Bush (Hymenoclea salsola), Buckwheats (Eriogonum spp.), Boxthorns (Lycium spp.), Mormon Tea (Ephedra spp.), Indigo Bush (Dalea fremontii) and various cacti are shrubs that commonly mingle with the Creosote Bush.
Soil conditions vary with respect to amount, alkalinity, and salinity. Shadscale scrub occur in the dryer, more alkaline parts of the Mojave. Though most of the members of this community do not occur widely in the Colorado Desert, a few new participants, such as Allscale (Atriplex polycarpa) and Desert Holly (Atriplex hymenelytra), join the group that rarely grow in the Great Basin. In salty areas Inkweed (Suaeda moquinii) and Parry Saltbush (Atriplex parryi) enter the mix, and Desert Salt Grass (Distichlis spicata) and Big Greasewood (Sarcobatus vermiculatus) indicate soil with very high concentrations of minerals.
At higher elevations of the Mojave Desert between 2,500 and 5,000 feet, Joshua Trees (Yucca brevifolia) span the gap between the Pinyon-Juniper woodlands and the lower Creosote Bush scrub. Joshua Trees will join both communities at their margins, becoming part of the woodlands or forming a sparse upper story, casting a shadow on the Creosote Bush undercover.
Desert annuals survive the hot, dry times as seeds. When the rains come, and where the soil is adequate, annuals like Rattlesnake Weed (Euphorbia albomarginata), Calico Plant (Langloisia matthewsii), Desert Star (Monoptilon bellioides), Nama (Nama demissum), and Chinch Weed (Pectis papposa) sprout and live for a few weeks or months as plants before scattering seeds that will be the next generation. During their brief blooming period, the flower show may, or may not be spectacular, largely depending on the weather. Generally the more rain that falls, the better, but how and when it comes is also important. Several small storms spread from November through February is much more helpful than one big one in October. Several soaking rains, spread over the Winter is best.