Many visitors are surprised at the amount of vegetation in Canyonlands. Plants are critical components to all ecosystems, and Canyonlands is no exception. Plants capture particulate dust in the air, filter gaseous pollutants, convert carbon dioxide to oxygen, provide animal habitat and possess many raw materials useful to humans. Many adaptations in leaves and roots enable plants to survive the extremes of temperature and aridity found in Canyonlands. These adaptations are grouped in three categories: drought escapers, drought resistors and drought evaders.
Drought escapers are plants that make use of favorable growing conditions when they exist. These plants are usually annuals that grow only when enough water is available. Seeds may lie dormant for years if conditions are not favorable. Spring annual wildflowers are escapers. They sprout following winter and early spring rains, and sometimes again after late summer rains.
Drought resistors are typically perennials. Many have small, spiny leaves that reduce the impact of solar radiation, and some may drop their leaves if water is unavailable. Spines and hairy leaves act to reduce exposure to air currents and solar radiation, limiting the amount of water lost to evaporation. Cacti, yuccas and mosses are examples of drought resistors. Yuccas have extensive taproots that are able to use water beyond the reach of other plants. Moss, a plant not commonly associated with deserts, thrives because it can tolerate complete dehydration: when rains finally return, mosses green up immediately.
Another extreme adaptation can be found in the Utah juniper, one of the most common trees in the southwest. During a drought, junipers can self-prune, diverting fluids from one or more their branches in order to conserve enough water for the tree to survive.
Drought evaders, the final group, survive in riparian areas where water is plentiful. Monkey flower, columbine and maidenhair fern are found in well-shaded alcoves near seeps or dripping springs. Cottonwoods and willows require a lot of water, and only grow along river corridors and intermittent streams where their roots can reach the water table easily.