The vegetation types in Colorado National Monument are a combination of pinyon pine, juniper, sagebrush, native grasses, desert shrubs, and limited riparian species. A coverage of 75 percent pinyon-juniper dominates the mesa tops with scattered sage-grass meadows. The canyon floors exhibit more of a mixture of pinyon-juniper, sagebrush, and desert shrubs.
Pinyon - Pinyon pine produce large edible seeds thus the scientific name Pinus edulis. Seed production is infrequent in the monument. Winter moisture is ample for the trees to produce male cones for pollen and for female cones to set seed. The summers are usually too dry, thus while the cones have grown, some of the seeds will be aborted. All that is found is a dried up scale in the cone. When there is a crop, squirrels and pinyon jays have a feast.
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.
