Popular Science Monthly/Volume 87/July 1915/The Floral Features of California
|THE FLORAL FEATURES OF CALIFORNIA|
ASSOCIATE PROFESSOR OF BOTANY. STANFORD UNIVERSITY
SHUT off from eastern North American by the high Sierra wall, that formidable barrier to the eastern and western migration of plant, as well as animal life, and possessing a climate unlike that of any other part of the continent, California has developed a flora that is unique. Indeed, isolation has been so complete that the California flora, with its host of peculiar or endemic species and even genera, displays many qualities characteristic of an insular flora, such as one might expect to find on a remote oceanic island. To the traveler familiar with the flora of the Mississippi Valley or of the Atlantic States, California plants seem as foreign as those of southern Europe. Species of such well known genera as Quercus, Prunus and Rhamnus (the oak, the cherry and the buckthorn) are so unlike their eastern relatives in foliage and general aspect that their true relationship is revealed only on close scrutiny.
But if the Sierra wall with its snow-clad summits has been an effective barrier to the eastern and western migration of plants, it has been likewise effective as a pathway for the southern migration of northern plants. And the warm valleys and foothills that lie at its base have been similar pathways for the northern migration of southern types. We find, therefore, the California flora composed of three distinct elements, the Californian, the Boreal, and the Mexican.
The Californian element, as recently discovered fossils prove, was established before the Glacial Period, and through its preservation from the destructive ice sheet, California has been able to hand down such a priceless heritage as the sequoias, an all but extinct race that at one time flourished over North America, Europe and Asia, extending as far north as Greenland and Spitzbergen. With the sequoias have come down many other conifers, making the California coniferous forests the richest in the world.
The Boreal or northern element, pushed southward by the ice sheet of the Glacial Period, formed a belt on the California mountains below 5,000 to 8,000 feet, the perpetual snow line of the ice age. At the end of the period, the ice retreated upward and northward, followed by the boreal plants, with the result that we now have arctic and subarctic species stranded on mountain tops a thousand miles or more south of their general range.
The Mexican element has migrated, largely since the Glacial Period, from the south through the desert and Great Basin regions following increased aridity. The great Mexican Plateau was the original home of most of the strictly American genera now found throughout arid and semiarid western America. On this plateau a drought-resisting flora existed in the Miocene age, when the greater part of the United States from the Atlantic to the Pacific was covered with a rich deciduous forest, comprising such trees as the beach, elm and magnolia—a type of flora that still persists in the southern Atlantic States.
The rôle played by climate in California has augmented that of isolation. Without its peculiarities and diversities the rich and varied California flora would never have been evolved. California climate is lauded the world over. Yet the term means little and is misleading as it carries the impression of uniform climate. Naturally within a state extending through more than nine degrees of latitude, 769 miles, one would expect to find considerable difference in the temperature of the northern and southern sections, with a corresponding difference in vegetation. But add to this range of latitude diversity of topography with its marked influence on rainfall, temperature and atmospheric humidity, and we have a complexity of climates and climatic influences that are astounding—literally scores of climates sufficiently distinct to influence profoundly the character of the vegetation.
Temperature, one of the most important factors governing plant distribution, ranges from the perpetual snow fields of the mountains to subtropical valleys where killing frosts are scarcely known. Bordering the snows of the high Sierra such boreal plants as the dwarf, arctic willow, cassiope, bryanthus, primulas and fringed gentians, flourish, while in the subtropical sections, the lime, the olive and the pomegranate are grown, and even the more sensitive though less poetic banana and alligator pear. Everywhere the African pelargoniums, the "geranium" cherished by the eastern housewife and tenderly nurtured within her furnace-heated house, runs riot, growing into good-sized shrubs and frequently used for porch coverings or hedges. The castor bean, described in all botanical text-books as an annual, here becomes a tree living for years, and grown for ornament and shade. Between these two extremes boreal and subtropical, are all "the intermediate zones; the cool temperate, where rye, red currants and apples flourish, and the warm temperate with the almond, apricot and fig.
But great as is the range of temperature and its effect on vegetation, rainfall and atmospheric humidity are fully as varied and play even a more important role over a large part of the state in determining the character of the vegetation. The normal annual rainfall in certain localities of the northwest coast region runs nearly to one hundred inches. At San Diego, also on the coast, it is only a little over nine inches. On the deserts, lying east of the mountains which have robbed the prevailing winds and storms of their moisture, the normal rainfall is seldom over five inches and often less than two.
With such a complex of climatic conditions it would be futile to attempt an account of the numerous plant associations or formations. We shall rather try to present some of the general features of the most important floral districts or belts.
The Coniferous Forests
California possesses the richest and most unique coniferous forests in the world. Nowhere is there the wealth of species and genera, nowhere such giant trees or interesting and rare types. Within the state there are thirteen genera and forty-eight species, twice the number found in the territory covered by Britton and Brown's "Illustrated Flora," an area over six times that of California. But it is not so much the variety of kinds that makes these forests famous as it is the grandeur of the individual trees, and the unique character or scarcity of the species.The Giant Sequoias or Big Trees are world-renowned for their immense size and great age—the oldest and largest living beings. Here, in their Sierran fastness, these giants stand majestic, vigorous and sound to the heart—trees that were centuries old when Christ was on earth. In the words of their first warden, the venerable Galen Clark,
They are distributed along the western slopes of the Sierra Nevada at middle elevations for a distance of about two hundred and fifty miles. Toward the southern end of their range extensive forests are formed and reproduce freely; but north of Kings River the groves are small and isolated, comprising middle-aged or mature trees with few or no seedlings. These isolated groves are thought to represent the original patches which escaped the destructive onslaught of the ice age. The average height of the large specimens is about two hundred and seventy-five feet, although trees three hundred and twenty-five feet have been measured. The diameter of the trunk averages about twenty feet, but a few trees attain thirty, and the General Grant is said to be forty feet at the much-enlarged base.
The Mariposa Grove and the smaller Tuolumne and Merced groves are within the Yosemite National Park. In addition to these, two other parks have been established by the Federal government for the preservation of the giant sequoia, the General Grant National Park, situated in the Kings River forest and the Sequoia National Park, in the Kaweah River forest.
Associated with the giant sequoias are to be found some of the best specimens of other Sierran conifers. Of these the sugar pine is the most magnificent. It is the king of pines. It attains a height of two hundred to two hundred and twenty feet, with a bole eight to twelve feet in diameter and often eighty feet to the first limb. The huge cones eighteen to twenty-six inches long hanging pendent from the tips of the widely spreading branches are a striking feature that marks the sugar pine as far as the eye can see.
In the redwood (Sequoia sempervirens) the giant sequoia (Sequoia gigantea) has a strong rival for first honors. The redwood is the highest known tree, the giant sequoia the greatest in diameter. Comparatively they stand about three hundred and fifty to three hundred and twenty-five feet in height, and twenty-two to thirty feet in diameter. The redwood is more abundant than the giant sequoia, and in the Humboldt forests it forms magnificent stands of timber from which over one million feet of lumber have been cut from one acre.
The distribution of the redwood is an excellent illustration of the delicate balance held between vegetation and climatic environment. It forms a distinct belt along the coast ranges of central and northern California, never extending inland more than twenty or thirty miles and conforming with striking significance to the coastal fog belt. The heavy summer fogs that frequent the coast ranges of central and northern California lower the temperature and increase the atmospheric humidity. Furthermore, the minute fog particles are collected on the forest trees and precipitated to the ground. The writer has tramped through fog in midsummer chilled to the marrow, with the trail muddy and slippery wherever it passed beneath a tree. Indeed, so great was the precipitation of the fog by trees that little rivulets formed and ran several yards down the mountain trail. Fifteen minutes' walk away the hot August sun was shining on a road inches thick in dust. Here were climatic differences as great as those of England and Spain.
Associated with the redwoods, but of more extended range are a number of other trees of special interest. The tanbark oak (Pasania densiflora) is the only representative in North America of that large Asiatic genus. Its acorns resemble those of an oak, but the staminate flowers are in dense erect catkins as in the chestnut, and with the same disagreeable odor. The California laurel, the only member of the genus Umbellularia, is a beautiful evergreen tree with smooth dark green lance-shaped leaves that emit the odor of bay. The madroñe (Arbutus menziesii), with its smooth polished trunks of a rich mahogany color, is one of the most striking trees in the California forests. It has attractive foliage of large, smooth, glossy, oval leaves, and bears open clusters of deep red berries that persist until Christmas.
In addition to the great forests of the Sierra Nevada and the redwood forests of the northern coast region, there are, usually in remote isolated spots, a number of other conifers especially interesting on account of their extreme rarity. All these species, which are far more local and rare than the giant sequoia, are situated in the coastal region. They are supposed to represent an ancient flora that existed here when the coast ranges formed an archipelago some distance off the western shore of the continent.
The Torrey pine is the rarest pine in the world. It is found only in two small groves of scattered trees, one a few miles north of San Diego, and the other on the eastern end of Santa Rosa Island. San Diego has wisely acquired the mainland grove and established a park in order that these trees might be preserved.
The Santa Lucia fir inhabits the Santa Lucia Mountains, an isolated range lying along the coast between Monterey and San Luis Obispo. This fir is found nowhere else, and is distinct from all other firs in its sharp-pointed leaves and bristly cones. It is within the Santa Lucia National Forest and is therefore assured protection.
Both the Monterey cypress and the Monterey pine are found on the Monterey Peninsnla. The pine forms a forest over a large part of the peninsula and extends down the coast for fifteen to twenty miles. There is also a grove on the coast of San Luis Obispo County and another a few miles north of Santa Cruz. The cypress is confined to two small groves situated on the two promontories that mark the boundary of Carmel Bay, just south of Monterey. Here, perched on the high cliffs overhanging the Pacific and buffeted by winds and storms into picturesque, often grotesque attitude, they add a Japanese touch to the charms of this coast, famed as the most beautiful spot on the Pacific. We are constrained to say that both of these groves are under private control. Cypress Point, the more accessible of the two, is in the hands of a self-styled "Improvement Company," and as we write word comes that it is to be surveyed into lots and thrown on the market. May public-spirited citizens do their utmost to acquire and preserve this unique grove! Surely it will be to our everlasting shame if California permits the destiny of these, the rarest of all trees, to depend upon the whims of summer cottagers.
Foothills and Valleys
Much of the peculiar charm of California lies in her rolling foothills and broad fertile valleys, purple-rimmed by mountains. Here are great stretches of the beautiful valley oak, with its massive spreading crown sometimes nearly one hundred feet across. To quote Dr. Sargent, the best known authority on American trees:
It is in the valleys and foothills that the typical California flora is seen in its full glory. Here poppies and buttercups, creamcups, tidy tips, yellow pansies, sun cups, yellow forget-me-nots, berries and bush mustard throw a gorgeous mozaic of mingled yellows over the coast meadows. In the open foothills, fields covered with splendid splashes of the wonderful gold of the poppy and the deep blue of the lupine, broken in spots by the gray green of the oak, spread out like a huge impressionistic canvas. On gentle slopes of sandy loam, escobita, cousin of the gaudy Indian paint brush, stretches out into a velvety carpet of old rose.
Typical also of the California flowers are the many varieties of bulbous plants curiously adapted to the California climate by their deep-seated bulbs that lie dormant through the long dry season, sending up their foliage leaves in early spring and their flower-stalks at the end of the rainy season. In the open fields and country roadsides the mariposa tulips, coming after the showy spring annuals, display large open cup-shaped flowers, delicately painted as a butterfly's wing. Brodiæas, some with open, others with close clusters of blue hyacinth-like flowers, greet one everywhere. Mission bells, mysteriously invisible, stand solitary tall and erect in the open woods, delighting their discoverer with drooping bell-shaped flowers mottled with bronze and green. Fairy lanterns, exquisite little plants of graceful form and delicate coloring, grow half concealed among the grasses of the open woods and rock ledges.
The advent of the white man has greatly changed the aspect of the vegetation in the valleys and foothills. Not only have vast fields of showy annuals, chaparral and noble oaks given way to orchards, vineyards and grain fields, but many of the open, unfilled foothills are now covered with wild oat, bur-clover or filaree, southern Europeans, brought over by the Spanish padres and spread broadcast by nomadic bands of sheep, which at the same time wiped out forever many a delicate native annual.
On dry gravelly hillsides, especially on southern exposures, and in the valleys where the soil is light and the water-table below the reach of roots, drought-resisting shrubs abound, forming dense, impenetrable thickets known as chaparral. These shrubs are evergreens with short, stiff, often spinescent branches and small, thick, leathery leaves of a dull gray or olive green. The level mass takes on a somber monotonous tone. But in blossom time, manzanitas with their tiny urn-shaped flowers of a delicate pink, lilacs forming masses of bine, lavender or white, garrya, with its long, pendant, soft gray catkins that have won it the name of "silk-tassel tree," the ever-present chamise, a peculiar rosaceous shrub with the foliage of the heath and spiræa-like clusters of small white flowers, the chaparral pea, mountain mahogany, bush poppy and yerba santa, all lend a charm that compensates for the long periods of gray monotony.
The preponderance of shrubs is a striking characteristic of California. One familiar with the shrubs of the eastern states will discover many surprises among the California varieties. To be sure, he will find many familiar genera, such as roses, currants and snowberries, but many strangers as well, such as the shrubby poppies, phloxes, mallows, monkey-flower, and even senecio. His solitary bear berry, uva-ursi, is here represented by about twenty species and New Jersey tea by over
thirty, many of which are very attractive in bloom and appropriately named California lilac.
In southern California the wild buckwheat, the laurel-leaved sumac and the black and white sage are prominent along the lower edge of the chaparral. The buckwheat and sages are bee plants par excellence, and produce tons of clear white honey. The Spanish-bayonet, a member of the yucca family, is widely distributed through the chaparral. Most of the year it is merely a tuft of dagger-like leaves, but in May and June each tuft sends up a straight flower-stalk eight to twelve feet high, bearing a huge pillar-like mass of creamy white flowers that may be seen for several miles. On canyon floors one will occasionally meet the matilija poppy. This is California's most gorgeous flower. It grows in round clumps eight to ten feet high, bearing a profusion of delicate crepe-like flowers, five to eight inches across, pure white in color with a rounded mass of yellow stamens in the center.
To transcontinental travelers the deserts are bleak, forbidding wastes, the very antithesis of life, and are passed with a shudder. But to him who follows their shifting trails with burro and pack saddle they open up a new world; animals, plants and the very rocks wholly unlike those of his well-trodden paths through fields and meadows. He may travel for days over the desert without meeting a familiar plant, no conifers, no oak, nor rose, no buttercups or violets. Plants, instead of spreading out broad green leaves to the friendly sunshine, protect themselves from the withering rays of a burning sun by casting off their leaves and forcing their twigs and branches to carry on their work, or by reducing the leaves in size and covering them either with wax, as does the creosote-bush, or with a dense layer of impervious cuticle, as does the desert holly, or with a gray mat of soft down, as do some of the daleas. Others, as the cacti, store up water in their thickened fleshy stems. Still others, members of the gourd family, develop enormous roots for water storage. Pondering on the significance of all these strange types, the wonderful adaptations, the development and modification of structures to meet these severe tests of endurance, one stands amazed at the powers of nature, realizing as never before the vital force of climatic environment.
Low, straggly shrubs of subdued tone and thorny cacti are the common plants of the desert. Of these the most universal is the creosote-bush with its waxy leaves, bright yellow flowers and all-pervading odor. Along living streams grow willows and cottonwoods, but desert trees are few in number. Where a little moisture is permanently retained, mesquit, palo verde and ironwood may be found. In the Mojave Desert the most striking feature is the yucca, which forms weird, fantastic groves scattered orchard-like over many square miles, the Joshua tree of the early Mormon settlers. On the western rim of the Colorado Desert, fringing the base of the southern California mountains, are several groves of the desert palm. An especially fine group is in Palm Cañon, splendid trees with straight, unbranched trunks eighty to one hundred feet high, crowned by great tufts of spreading fan-shaped leaves and clothed sometimes nearly to the base with withered leaves that lie pendant along the sides in great thatch-like masses. Here is a veritable Saharan oasis, and there eight miles away and ten thousand feet above, stands the summit of San Jacinto, harboring typical arctic plants around its lingering patches of snow.
Such are the contrasts of California.