Salvia dorrii and Artemisia tridentata

Habitats in Central Washington range from alpine and rainforest in the west, to dry ponderosa forests and shrub steppe to the east. A few plants can live in variety of conditions, and some are restricted to specific habitats. The plants that grow in the arid eastern region near the Columbia River and the Columbia Basin have a number of traits which help them to be successful in the desert.

Two of the main adaptations of plants in arid environments is having an economical water management system, and maximizing the energy gain from the process of photosynthesis.

Some plants, called xerophytes, have adapted their physical structure to suit the rigors such a harsh environment. These plants have adapted by having smaller leaves, grow compactly and close to the ground, and a non-porous covering on their leaves such as wax. Hair on the leaves of plants helps to reduce the evaporation of moisture from the surface of leaves by reflecting sunlight and inhibiting air movement. The process of photosynthesis requires both carbon dioxide and water to create energy for the plant. Water is usually absorbed through the roots, and carbon dioxide is absorbed through tiny pores in the plant called stomata. Through the stomata the plant is able to obtain carbon dioxide, but it also loses water by evaporation when the pores are open. Some plants cope with the water loss problem by having fewer stomata, or by having the stomata only open at night when it is cooler. All of these adaptations help to reduce evaporation and transpiration of water.

Eriogonum heracleoides

Differences in cellular structure and function, as well as in the basic process of creating carbohydrates from water and carbon dioxide also help plants to survive in arid conditions. The common process of photosynthesis is called the C3 cycle because carbon is fixed by the plant into a three carbon compound (phosphoglyceric acid) in order to make carbohydrates. Another process of photosynthesis used by desert plants such as bunchgrass fixes the carbon into a four carbon compound (malate or aspartate acid). This C4 process, although not used by many plants, is more efficient in maximizing energy gain than normal photosynthesis.

Succulent plants such as stonecrop (Sedum spp.) and cactus can store water in the specialized tissues of plant cells called vacuoles. Some desert plants the cells, unlike in the ordinary varieties of cultivated plants, can also survive extreme dehyration then rehydrate when water is available with little or no damage to the cells.

Other plants, called phreatophytes, have adapted root systems that are long enough to reach underground water sources. An example of an extensive root system is the tall sagebrush (Artemisia tridentata), whose roots can grow up to 25 meters in diameter. Because tall sagebrush is able to utilize underground water sources it can remain photosynthetic throughout the summer, and is one of the latest blooming of all plants in the Columbia Basin.

Lomatium macrocarpum

Other plants cope with the extremes in temperature and rainfall by becoming dormant during the winter or droughts, and escaping difficult times all together. Annuals and ephemerals grow only when conditions are at optimum. Some seeds can remain dormant for years and even decades, waiting to germinate when the conditions are favorable.

Members of the Lilicae family and others such as the genus Lomatium, store energy within their roots when they bloom in spring and set seed. This stored energy is enough to survive for most of the year in a dormant state. By late summer the upper parts of the plant and leaves dry out above the ground, leaving none of the plant's soft tissues exposed to heat and dryness of summer. By the middle of summer many plants in a desert environment are dormant, and show few signs of life.

Another strategy of drought avoidance can be seen near any stream or wet area. Some plants only germinate and grow in riparian areas, forming the stark contrast in vegetation seen near any water source in arid regions.

Erigeron linearis /Desert Yellow Daisy blooming in early spring. This plant has small linear leaves, that are also hairy and almost succulent; all of these attributes help the plant cope with harsh desert temperatures. This plant is common in Central Washington on south facing slopes at lower elevations.