Plants

Plants

Vegetation within the monument and surrounding lands is primarily pinyon-juniper woodland, which receives less than 12 inches (28 cm) average annual precipitation. Woodland trees are usually less than 20 to 30 feet tall (6 to 9 m). Shrubs associated with this woodland include rabbitbrush, big sagebrush, single-leaf ash, broom snakeweed, Utah serviceberry, yucca, Mormon tea, mountain mahogany and cliff rose among others.

Prickly Pear

The common prickly pear cactus is one indicator of land health. The area of lowest precipitation with the most easily disturbed soils are along the northeastern boundary (urban interface). The dominant vegetation consists of galleta (Pleuraphis jamesii) - a native grass, prickly pear cactus, and annual weeds. When buffalo were in the monument this area was over-grazed and trampled. With grasses removed the cacti took over making it hard to walk across the ground with out continually stepping on cactus plants. After removal of the buffalo, galleta began to come back. In wetter years this grass grows tall enough to out compete cactus for sunlight. This competition has reduced the cactus to a reasonable distribution.

Prickly pear is an important native plant. It is a protective site for a rodent to burrow under. During drought years they are an important food source for grazing animals. During wetter years the largest species of prickly pear produces a red fruit that is as good and sweet as an apple or pear. This fruit is highly prized by coyotes and a treat for the knowledgeable hiker.

Prickly pear pads are enlarged and have flattened stems. Their function is photosynthesis (energy capture and food production). They also store food and water. The spines grow from the point that produces leaves in other plants. The pads have a wax coating that masks the bright green underneath. The darker green would absorb too much light and cause the plant to cook under intense sunlight on a hot summer day. As the pad dries and shrinks in size during drought, the wax surface wrinkles producing an even duller color. During dry periods some pads take on a reddish color which protects the plant from ultra violet light. Stems will on the average produce a new pad each year and the pad lives for around ten years. As the old pads die the newer pads can send down roots so the plant can continue mining for nutrients and water.

During late spring and early summer these plants put on a great show. The flowers are large with waxy appearing petals. The flowers can be yellow-green, yellow, bronze, pink or violet.

In the center is one bright green stigma surrounded by hundreds of stamens. The stamens are touch sensitive and curl in on beetles as they forage within the flower. This covers the beetles with pollen that they carry to the next cactus blossom.

Wildflowers

A wide variety of species await the visitor from the lower sagebrush community, through the pinyon-juniper woodland and up to the oak transition zone. Individual species differ in number each year according to rainfall and weather conditions micro-ecosystems abound as topography offers a wide gamut of growing conditions. Tall south-facing sandstone cliffs offer protection and warmth allowing the opportunity to discover flowering plants year-round. Seep and springs encircled by rock bluffs protect lush fern gardens.

The desert annuals have adapted to the arid environment through a series of different strategies. Many plants, including wildflowers like the hairy goldenaster, have small leaves to reduce the amount of transpiration with “hairs” to interrupt wind flow and shade the leaf’s surface. Other flowering plants like the desert four o’clock have developed thick, waxy coverings on the leaves and stems to reduce the amount of water loss.

Flowers bloom during the wetter spring and fall seasons and avoid the summer heat and drought. Using another strategy, some plants like evening primrose, often seen along Rim Rock Drive, bloom during the cooler evenings and nights and are pollinated by night flying insects such as moths.

Trees and Shrubs

Pinyon trees are very resinous. During the hottest times of summer the trees dry out. The combination of dry wood and resin makes them very flammable. When they burn they produce very hot and fast moving fires.

Juniper (Juniperus osteosperma)- Junipers produce a cone that is a blue wax covered berry-like structure. These cones are poisonous to most animals and are a rich food source to others such as the cedar waxwing. The older junipers in our park are often infected with mistletoe. Mistletoe is a plant that is parasitic on junipers. It feeds on the tissues just below the bark and eventually kills the tree. Birds eat the sticky mistletoe berries. Berries that stick to the outside of their beak are removed by brushing their bill back and fourth on a tree branch. In doing this they have planted the seed on the limb of another tree.

Older junipers have character with their large twisted and misshapen trunks. The transport tissues on one side of a tree may die shifting all growth and transport of water, nutrients, and sap to the other side of the tree. Other transport tissues die, further distorting the trunk.

Juniper trees can withstand an inch or two less precipitation per year than pine trees. This is why the tree line that extends into desert is of junipers only. The juniper is like the pine in that as it ages, vegetation on the forest floor is greatly reduced. These trees also produce very hot forest fires that can move fast.

Singleleaf ash (Fraxinus anomala) - This is the only native broadleaf tree that grows in our semi-desert climate. It is a dwarf tree that normally is less than 15 feet tall. These trees are found where a little extra water collects. In springs of good moisture they produce an abundance of single winged seeds.

Shrubs - Mesa tops are covered with pinyon-juniper forests that have open areas composed of sagebrush (Artemisia tridentata) with some rabbit brush (Chrysothamnus nauseosus) are known as sage flats. These shrub areas support several native grasses such as galleta (Pleuraphis jamesii),Indian ricegrass (Achnatheram hymenoides), and needle and thread grass (hesperostipa comata). Scattered among this vegetation are small white daisies, orange poppy mallow, and purple vetches.

Above 6,000 feet, steep rocky hillsides are typically covered by mountain mahogany (Cercocarpus montanus), sagebrush, and serviceberry (Amelanchier utahensis) with smaller shade loving snowberry (Symphoricarpos oreophilus) growing under them.

Seasonal drainages can provide a habitat for vegetation more typically seen in riparian zones. Fremont's cottonwood (Populus fremontii), coyote willow (Salix exigua), and tamarisk (Tamarix ramosissima) can be seen in various locations throughout the park but are perhaps most prominent in Ute and No Thoroughfare Canyon.

Scattered cottonwood and coyote willow is the dominant vegetation. Growing under them are sedges, rushes, and scouring rush. In the few places where there are small pools, cattails (Typha domingensis) are found.

Dense shade loving shrubs like mountain mahogany, alder (Alnus incana), wild rose (Rosa woodsii), and Apache plume (Clematis ligusticifolia) vines are common in the box canyons of the monument.

Cacti / Desert Succulents

Colorado National Monument sits on the eastern edge of the Great Basin Desert. Unlike the more familiar deserts farther south, the hot arid summers in the Great Basin give way to freezing cold winter conditions. This presents some special challenges to the survival of succulent plants such as cacti.

Succulent plants have evolved the ability to quickly store water in specialized spongy tissues whenever moisture becomes available for use later in times of drought. This ability to store water can, however, create a serious plant survival problem during freezing cold weather. Moisture within the succulent plant tissues freezes, causing severe damage or death to the plant.

As winter approaches, cacti of the Great Basin Desert are able to reduce the moisture in their tissues to the point that they shrivel and go limp; some actually shrink down into the soil. The moisture remaining in the plant is altered so that the succulent plant tissues are not injured by freezing.

The return of spring warmth and moisture is all that's necessary for these cold climate cacti to quickly and fully recover from winter dormancy.

Cacti are the most abundant type of succulent plant within Colorado National Monument. Visitors may find the following species:

• Missouri Pincushion (Escobaria missouriensis)
• Porcupine Prickly Pear (Opuntia erinacea)
• Brittle Cactus (Opuntia fragilis)
• Purple-Fruited Prickly Pear (Opuntia phaeacantha)
• Cliff Prickly Pear (Opuntia rhodantha)
• Mountain Ball Cactus (Pediocactus simpsonii)
• Eagle Claw (Sclerocactus parviflorus)
• Claret Cup Cactus (Echinocereus triglochidiatus)
• Spineless Hedgehog Cactus (Echinocereus triglochidiatus forma inermis)

Photographs and descriptions of most of the cacti listed above can be found in the following books sold at the visitor center:

Simon and Schuster's Guide to Cacti and Succulents, edited by Stanley Schuler.

Cacti of the Desert Southwest by Meg Quinn

Most species are scattered throughout the monument, a few have more restricted habitats. Mountain Ball Cacti grow at the higher elevations. Missouri Pincushions and Spineless Hedgehogs are found in the southeastern portion of the monument.

The flowering season begins in the lower elevations in mid April, continuing into early July at higher elevations.