Desert plant

“ A quaint little desert plant, only two or three inches tall, with thickish, pale gray-green leaves, covered with close white down, and pretty little flowers, growing singly at the ends of tiny branches, each half an inch across, with a yellow center and pure white rays, which fold back at night. These little flowers are too small to be very conspicuous, but are charming in effect, sprinkled over the bare sand, and when growing in quantities on nearly bare mesas give a whitish appearance to the ground. ”

“ Leafless shrubs and trees whose often spiny branches are green and perform, on a much-reduced scale, the function of leaves, are among the most common characteristics of desert plants. Some, as Parkinsonia microphylla or paloverde, have tiny leaves which they put out during the spring showers, but quickly lose them as it gets hotter and drier toward midsummer. Many of the plants that do produce leaves regularly have the surface of them so shiny as to appear varnished, or so thickly coated with hairs as to simulate cotton or wool, both of which reduce transpiration. ”

“ Where, as in an oasis in the desert, water is locally plentiful a luxuriant vegetation springs up, and one of the most fertile parts of our Southwest was transformed from a desert by irrigation. Then, too, in many deserts there is a pronounced rainy season during which there is a marvelous development of showy flowering herbs that die down as rain ceases or becomes too slight, to wait for another opportunity to make the desert blossom into often gorgeous coloring. ”

“ To find plants growing in desert places we do not need to go out of England, because from the point of view of the plant, one which is growing on a dry rock or on a patch of bare dry sand, is really growing in a little desert. For it the supply of water is the chief problem, even though we never get hot tropical sunshine in England. Look, for example, at the plants growing on the sand dunes which are very like deserts in appearance, and the plants on dry walls, or on the “screes” of broken rock at a hill foot; they are all growing in deserts. ”

“ Although our own country, favoured by conditions thoroughly suitable to plant life—a sufficiently high temperature and an abundance of moisture and light—is characterized by a continuous plant mantle—or closed vegetation, as the botanists say—nevertheless what has been said of desert and semi-desert conditions applies to many limited areas in the British Isles, where the vegetation takes on the peculiar characters of true desert plants. Low water-content and great exposure produce such conditions on shingle beaches and sand dunes ”

“ Many desert plants are built on the plan of the cactus, but there are also others which are not at all like them, and yet they are able to live in deserts and very dry places. It you examine them, however, you will find that they all have some special way of protecting themselves from being dried up. Some of them have hard, dry, woody stems, well protected by corky layers, and they only put out green leaves in the rainy season, and lose them directly the hottest weather begins. ”

“ When it congeals it forms a gum which heals over the wound and once more prevents evaporation. Existence for the plants would be impossible without such inventions. Plant life of every kind requires some moisture all the time. It is an error to suppose because they grow in the so-called “rainless desert” that therefore they exist without water. They gather and husband it during wet periods for use during dry periods, and in doing so they seem to display almost as much intelligence as a squirrel or an ant does in storing food for winter consumption.
Attacks upon desert plants. ”

“ Soil composition, slope and exposure, suitable temperatures, and adequate moisture are essential to plant growth and flower production.
Moisture is the uncertain factor, and years may pass without enough rainfall to stimulate plant growth. Rain of less than 0.15 inch is wasted as far as desert plants are concerned, for the moisture evaporates before penetrating the soil. Some annuals produce seeds having water-soluble germination inhibitors in their coverings, hence fail to sprout, even after rain, unless the moisture totals at least half an inch. ”

“ Almost any ordinary branching plant with broad leaves will, if forced to carry out its development under arid conditions, show some of the features of the type of desert plants described, and it is customary to assume that the causal conditions responsible for such forms are the desert factors: that we have here a direct adaptation or environic response which has become heritable in the strictest and fullest sense. ”

“ This is not an uncommon occurrence with desert plants. For example, whenever in the Tucson region the arid seasons are uncommonly long, or there has been a relatively small rain, as 25 per cent less than usual, much of the vegetation may remain dormant. Under such conditions an evergreen like Covillea tridentata drops all save the youngest and smallest leaves and maintains this nearly defoliate condition for long periods, with little other change. The plant behavior noted is always connected with insufficient moisture. ”

“ Often, too, the upper surface is almost flattened, while the main part of the plant is a carrot-shaped fleshy root, which Nature, the great Builder, has made a reservoir of food and water for this, her baby of the Fantastic Clan, to withstand the drying desert winds that sweep across the mesas and up the cañons, and the months of drought and fiery heat in the desert sun, when no rains come to freshen and beautify the earth and to gladden the hearts of native dwellers on the desert. ”

“ Under such conditions it is not surprising that desert plants are among the most curious and weird members of the plant world. Every device both to retard transpiration and to store up water to last over a completely rainless period, may be found. ”

“ Such regions produce a desert type of vegetation and are popularly, if not properly, called deserts. The largest is of course the Sahara in Africa, but there are huge tracts in Arabia, China, Thibet, Australia, South Africa, and in some other countries where the conditions for plant life are so unfavorable that only in the better sites are plants found at all. In all deserts there are very large areas entirely without plants, due to shifting sand or other local conditions, which, added to the generally unfavorable climate, make plant life impossible. ”

“ It is one of the commonest, queerest, and most spectacular of desert plants, especially when the tips of its long, slender stems seem afire with dense clusters of bright red blossoms. Following rains, leaves clothe the thorny stems with green, but after the soil becomes dry, the leaves turn brown and fall. The heavily thorned stems are covered with green bark which takes over the functions of leaves during periods of drought. ”

“ But before we pass to the consideration of the conditions where favourable environment results in a closed vegetation, we may suggest for consideration the following point of view: that for any plant, or group of plants with similar requirements, much of the world is a desert—that is, a place where conditions are such that it cannot live. ”

“ The plain, at first view, with a covering of small stones and pebbles, gives the impression of total barrenness. Not a tree, shrub, or herb appears to hide the bare ground. The mountains are naked rock, while the harsh outline of desert ranges and the distant low sand ridges give no evidence of plant life. But a closer examination of plain, dune, and mountains reveals the presence either of living forms or of the dried remains of plants of a preceding moist season, in numbers and in kinds not at first suspected. ”

“ CACTUS GROWTHS OF THE DESERT.
mammoth sea-weed. The "grease-wood" is a large bush, said to burn just as well when green as dry. Most of this vegetation is leafless, or rather the plant seems a leaf itself, since coarse bark is lacking, and the green of chlorophyll and the tenderness of structure seem equally distributed throughout.
There are homely legends and superstitions about these plants of the desert. A certain one, for instance, poisons any white spot on a horse, but not one of any other color. Another, eaten by horses, makes them lazy and imbecile. ”

“ To one who has the opportunity of visiting the Desert, the flora will at once appear striking and in many respects different from that inhabiting other more favoured provinces. The general barrenness of the country, the dry practically rainless climate and the scorching heat of the sun, not to omit the general usceptibility to the wind, have so modified the external organs of the desert plants, that it is but natural to conclude that the internal structure and the processes that are going on in the plants must in like way have been acted upon by these external factors. ”

“ Seldom does the desert herb attain the full stature of the type. Extreme aridity and extreme altitude have the same dwarfing effect, so that we find in the high Sierras and in Death Valley related species in miniature that reach a comely growth in mean temperatures. Very fertile are the desert plants in expedients to prevent evaporation, turning their foliage edge-wise toward the sun, growing silky hairs, exuding viscid gum. The wind, which has a long sweep, harries and helps them. ”

“ Most desert plants are drought- or salt-tolerant. Some store water in their leaves, roots, and stems. Other desert plants have long tap roots that penetrate the water table, anchor the soil, and control erosion. ”

“ The lower elevations and flatter areas of the monument contain the creosote-bursage plant community. This plant community thrives in the open expanses between the mountain ranges, and connects the other plant communities together. Rare patches of desert grassland can also be found throughout the monument, especially in the Sand Tank Mountains area. The washes in the area support a much denser vegetation community than the surrounding desert, including mesquite, ironwood, paloverde, desert honeysuckle, chuperosa, and desert willow, as well as a variety of herbaceous plants. ”

“ In favorable years these ground-hugging plants form broad, colorful mats, but in dry seasons these annuals may be tiny, each with a single flower almost as large as the rest of the plant. Flowering from February to May, bloom is heaviest in March and April. This species, also called “purplemat,” is common on flat, sandy, open desert soils from southeastern California and Baja California to southeastern Arizona at elevations below 3,500 feet. ”

“ Also called “sun-drops,” these plants are particularly welcome because they bloom early in the springtime. Many species of evening-primrose are large flowered, abundant along roadsides and sandy flats, and notably fragrant. White-flowered species are more common, but there are several with yellow flowers. Blossoms open at night and begin to wilt, turning pink during the following day. These are among the handsomest of desert plants and during favorable years make a spectacular spring display, sometimes growing with goldpoppies and sandverbenas to produce a riot of color. ”

“ Along springs and sunken watercourses one is surprised to find such water-loving plants as grow widely in moist ground, but the true desert breeds its own kind, each in its particular habitat. The angle of the slope, the frontage of a hill, the structure of the soil determines the plant. South-looking hills are nearly bare, and the lower tree-line higher here by a thousand feet. Cañons running east and west will have one wall naked and one clothed. ”

“ For the desert is hotter and drier in some places than in others. The gradual downslope changes in vegetation reflect the decrease in the amount of soil moisture available to plants—a condition caused by the decreasing size of soil particles and consequent shrinkage of water-holding space between particles. Desert washes encourage plant growth because they channel water and cold air. Strangely enough, night temperatures are often lower in a desert valley than farther up the slopes. ”

“ The Parry Nolina of the California Desert is a larger and more spectacular plant than the species found in the Arizona and Texas-New Mexico Deserts. Indians are reported to use the very young flower stalks for food. Leaves are browsed by livestock in times of drought, sometimes with harmful results in the case of sheep or goats. ”

“ Although cacti are often thought of as characteristic desert plants, other types of plants have adapted well to the arid environment. They include the pea family and sunflower family. Cold deserts have grasses and shrubs as dominant vegetation. ”

“ Where the conditions are especially unfavourable to plant life, we find that even the grassland plants are unable to keep up the struggle, and diminish in number, losing their power of forming a complete covering for the soil, and thus the grassland passes into desert, whether the hot waterless desert of low latitudes, or the cold frozen desert of northern ones. ”

“ Most of our common British plants occur along the shore of the Black Sea to the Caucasus (apple, pear, nut, turnip, cabbage, carrot, and others, are all probably to be found there) . On the Babylonian side of the mountains, there is a warm sub-tropical climate in which almost every useful plant can be grown. The desert also contains a few other valuable plants. ”