Part 2

PLAINS

All of Colorado lying east of the base of the mountains, as well as large areas in western Colorado lying along the course of the Colorado River and its main tributaries, are within the life zone commonly known as the Plains, and referred to in technical books as Upper Sonoran. These areas are mainly below 5500 feet in elevation, and are relatively flat. Clay soils are the rule, with local sandy spots. The rainfall throughout this zone is scanty and irrigation essential to general farming. These conditions have restricted the native vegetation throughout this zone to species which can tolerate long periods of drought, and thrive on sunshine with heat in summer and cold in winter. A surprising number of species of flowering plants live and thrive on these very conditions. We rarely find them in colorful masses, single plants or small colonies being the rule.

Originally native grasses covered this zone with a fairly tight sod, broken, however, by windblown patches and cut by arroyos. Live streams were far apart. Trees were absent except for cottonwoods and a few box elders along water courses. Settlement has brought roads, ditches, cultivated fields and a large amount of livestock. These acts of man have made life hard for some native flowers, but for most species, living opportunity has been increased. The plains are flowerless only for those who fail to pause and search.

The detailed growth patterns or specialized mechanisms by which the various plains flowers resist drought, and so get a chance to live, are numerous. In general they do one or more of these things: rush through a short individual life cycle from seed to seed so timed that the new seed crop is set before the heat of summer is far advanced; conserve the limited moisture their roots gather by having few leaves and defending them from animals by thorns or toughness; or, spend a large part of every year, especially the dry, hot months, as a dormant bulb or buried root stock.

The picture at the top of this page shows a plains area just at the base of the foothills near Denver. It looks barren, but many species of flowers can be found there in May and June.

FOOTHILLS

Long strips of land from 5500 to 8000 feet in elevation lying between the plains and the mountains, and filling in with rough hills and valleys the spaces between mountain ranges, comprise a life zone known as the Foothills, and named, by naturalists, the Transition zone. In this zone much of the soil is filled with gravel and weathered rock detritus washed down from higher land or left there by ancient glaciers. Total annual rainfall in this zone is higher than on the plains, and the broken character of the land gives protection from storms.

A greater number of species of flowering plants can be found in this zone than in any other single zone. Local conditions of soil, water and sun exposure vary widely, and these variations offer favorable living conditions to different types of flowering plants and to the numerous shrubs that grow here. Many species of wild flowers which grow on the plains extend into the lower parts of this zone, while other species found in the higher mountains reach down into it, especially along streams.

The chief native trees of this zone are yellow pine and, along streams, narrow leaf cottonwood. Scrub oak covers many hillsides with dense growth, junipers are locally plentiful, and aspens reach down from higher elevations. This tree population attains forest proportions only here and there so that open places for wild flowers are abundant.

In Colorado, visible spring comes earlier in this zone than on the plains below. Sheltered slopes facing the sun pick up the earliest flush of spring green, and by the end of March the very first flowers may here be found in bloom. Late April, May and early June bring the main flower crop. Mass color effects may then be found such as several acres blue with Larkspur, or a whole hillside dotted with red clumps of Lambert’s Loco. The main show is over by mid-July, though asters and sunflower-like composites keep the roadsides colorful till frost.

The picture at the top of this page shows a foothills area near Golden. In good years these hills are rich in flowers by early May. A half hour walk then will frequently yield 30 species or more.

MONTANE

The great mid-sections of our high mountains, lying between 8,000 and 10,000 feet in elevation, make up a life zone called Montane, also known as Canadian. Since most of our Colorado mountains are granite, the typical soils in this zone are granite gravel. Some mountains, however, are faulted blocks of sedimentary rock which have weathered into clay and sand soils. The annual rainfall in this zone is over double that of our plains. This has resulted in forests of lodgepole pine, aspens, and of several species of spruce, with stream banks lined with willows and water birch.

This abundance of vegetation has produced enough humus to build rich black soil in the bottoms of the narrow valleys. In this zone grow a wealth of flowering plants. The principal adverse conditions against which they struggle for existence are: a fairly short season from spring melt to fall freeze; and more tree shade and more competition from tree and shrub roots than they would choose. The steep hillsides in this zone may be quite rock covered. Between the rocks small amounts of good soil may form, and under loose rocks moisture stays for a long time. Trees thrive on these hillsides, but in open spots and beside rocky outcrops flowers get their chance. The columbine grows in perfection in this zone, extending downward into the foothills and upward to timberline.

The building of highways in our mountain areas has introduced new conditions of which some plants are quick to take advantage. The stirred-up soil of new road fills and drainage channel construction will be colorful with fireweed, purple fringe, brown-eyed-susans, with here and there penstemons and asters by the second or third season of their use. Local irrigation accomplished by highway drainage and the use of snowplows, as well as distribution of seeds by animals and even by cars that use the roads, all play their part in this quick restoration of life in the soil that has been torn up.

The picture at the top of this page was taken near Mary’s Lake in Estes Park. The mountain shown is Twin Sisters. Its slopes are a fine hunting ground for flowers.

SUB-ALPINE

Above 10,000 feet the pattern of life changes. Until timberline is reached at about 11,500 feet, this band of mountain country is called the Sub-Alpine or Hudsonian life zone. Soil and moisture conditions are almost as favorable as in the lower montane zone, but here the snows of winter stay late, especially on north slopes, and frost may come even in mid-summer. The race to ripen seed, before winter comes, is intense, and the seeds, when produced and scattered, face special problems of germination and survival.

The trees of this zone are largely Engelmann spruce, limber pine and alpine fir. Some thick forest stands exist, but the main pattern is small compact tree groups—one or more big seed-trees surrounded by younger offspring—with open patches of grass between. Perennial flowering plants, springing from woody root-crowns have special advantages here, though some annuals thrive, especially if they can get started in the fall and remain dormant under snow till spring. Melting snows in May, June and early July give natural irrigation to large areas of this zone. Competition with sedges and grasses and ability to stand light frost are problems for the plants that live here. Many typical alpine plants of the next higher zone work down into these sub-alpine meadows.

The picture at the top of this page was taken just west of the Poudre Lakes in Rocky Mountain National Park. Lake Irene is in the foreground.

ALPINE

From timberline (about 11,500 feet) up to our highest Colorado mountain summit (Mt. Elbert 14,431 feet) climate is too severe for any trees. This condition marks these areas off as a separate life zone called Alpine or Arctic. Soil forms only slowly on these rocky summits, but mosses, lichens, sedges and grasses have been here for ages of time, all of them patiently building humus. Erosion carries less soil away from the tops than it does from the lower hillsides. So in the spaces between the barren looking rocks, good soil exists, and water, though mainly falling as snow, and not quite as heavily as in the sub-alpine zone below, is adequate for plants. Here grasses, sedges, a few dwarf shrubs and herbaceous plants have all the sunlight to themselves without tree competition. The ever-present adverse condition is low temperature, frequently with strong wind.

It is a land of tough dwarf things. Perennials are the rule, though annuals are found. Low woody mats with basal leaves and flowers only a few inches high are a common pattern. Bulbs and tubers wedge themselves between rocks, out of reach of ground squirrels, if possible. When spring comes with a rush, usually late in June, these dormant plants burst into life in the days of longest sunshine. Shoots of new growth erupt from the ground with buds all formed ready to open. By the end of July the seed crop is largely mature, and by mid-August the browns and crimsons of fall colors in leaves and grasses spread a Persian carpet over these heights. Warm days from then till winter are days of germination for newly scattered seeds and, for established plants, preparation of buds for next year.

It is in this zone of harsh living conditions that some individual plants probably attain greater age than is normally reached by plants of the lower life zones. We know of no statistical study to support this statement, but observation of mats of moss campion, or of tufts of alpine spring beauty, or of scarred old crowns of alpine forget-me-not, indicates that they have safely survived the snow cover of a great many alpine winters.

The view at the top of this page is from Trail Ridge in Rocky Mountain National Park. Longs Peak is in the distance. In mid-July these foreground slopes are a garden of alpine flowers.

Lily Family Sand Lily, Leucocrinum montanum, NUTT.

Flower is an inch in diameter, of 6 petals and sepals all alike (perianth segments) united at their base into a tube over an inch long. Several of these rise from the buried crown of the plant, as do also the leaves, ⅜ inch wide and over 6 inches long, resembling heavy curved blades of grass. The matted, cordlike roots store, through the long dormant period, the starches and sugars needed for rapid Spring growth. Grows in sandy soil in plains or low foothills. Blooms April-May.

When sand lilies begin to dot the gray plains with their singularly pure white stars we can know that the season of growth and color is returning. We called them Mayflowers and hoped they would be in bloom for May-baskets. They usually were—along with Johnny-jump-ups (little yellow violets) and sprays of pepper and salt parsley. To pluck them one by one and suck the drop of nectar from the long white tube is one of the delights of childhood. The plants are crowded with flowers during the blooming season, but, when it is over, disappear completely from the scene.