The methods used by plants in adapting to arid conditions are interesting and varied. The wide-spreading, shallow root system and thick stem of the cactus enhance collection and storage of water. These strange plants are quite plump with stored water in the spring when the snows melt, but they gradually lose this plumpness during the dry summer, and by autumn many seem lifeless.
Other plants conserve their water by minimizing the loss through their leaves. This may be done in a number of ways. The leaves of the spiny greasewood are covered with a waxy substance that inhibits water loss while the leaves of the sagebrush are covered with hairs or fuzz that serve the same function. The leaves of the juniper are scale-like and really don’t look like leaves at all. The most direct method of preventing water loss through leaves is to drop the leaves themselves, and this method is used to a greater or lesser degree by many desert plants. The serviceberry is a good example of this method. In late summer it looks dead, and yet the following spring finds it robed in green and covered with flowers.
In contrast to the frugal habits of the plants just described, the cottonwoods seem lavish indeed. Usually big trees, they spread a canopy of green in whose shade rest birds and animals alike. Have you ever rested under a cottonwood? If so, you will remember it as being cool even on the hottest days. Part of the coolness was due to the hundreds of gallons of water which are transpired through the leaves each day. Because cottonwoods require so much water, they usually grow along streams or near springs. Frequently they are seen along dry ravines where their thirsty roots tap the subsurface drainage that lies hidden below. Like the other plants however, when the supply of water becomes inadequate they shed their leaves and wait for the next spring. Fast growing, usually of large size, and wasteful of water where water is dear, the cottonwood seldom lives two hundred years while the twisted juniper on the dry, rocky ledge frequently lives as much as five hundred.
SPLIT MOUNTAIN GORGE.
Inconspicuous through most of the year are the flowering plants. Some of these are annuals—plants that grow from seeds, mature, bloom, produce seeds, and die in the span of a few short weeks. When the snows melt and the sun warms the earth, the seeds that survived the winter germinate. The usually barren hillsides produce spots of green that soon spread to form patches as more and more plants mature. Lupine and locoweed are purple and heliotrope splashes color along the roads, while the fragrant, white, evening-primrose dots the sandy hillside. Scarlet gilia and Indian paintbrush add a touch of red to the scene, and orange is provided by the mallow.
April, May, and early June provide the best flower show as spring rains supplement the moisture from melted snow. Their races won, their seeds produced, the annuals wither and fade away as the temperatures rise. By the first of July little remains of the splendid show.
Two plants do brighten the desert scene in August and September. Most common is the rabbitbrush, a plant that grows almost everywhere. It is rather inconspicuous except in late summer when its brilliant yellow blossoms turn the whole shrub golden. The other is the bee plant of which there are two species: one has yellow blossoms, and the other has purple. These tall plants grow along washes, stream courses, roads, and irrigation ditches. Their delicate blossoms are always surrounded by insects drawn by the nectar the flowers produce in great quantities.
These, then, are a few of the typical plants. Each has adjusted its needs to those limiting factors—winter cold, summer heat, and aridity. A great number of plants grow on the monument that have not been mentioned here, but they are like the typical plants and have similar ways of meeting the problems of survival.
Many people who profess an interest in nature admit they cannot get very excited about plants. Such disinterest may result in minimizing the importance of plants in the general scheme of nature. That would be a major error. The plants of the world are the foundation upon which other forms of life are dependent. They alone are able to utilize the minerals in the soil and convert carbon dioxide and water to carbohydrates. Because of these abilities, the parade of life has been able to advance only when the plants advance. In the present as in the past, the kinds and abundance of plants set definite limits as to the species and numbers of animals an area may support. Thus, if man changes the plants of an area he will surely change the animals too, whether he realizes it or not.