Plants are an important resource in Idaho. They provide food and shelter to animals, cleanse water in watersheds and offer ground cover for protecting water and wind erosion. Idaho has roughly 3,000 plant species, according to the City-Data website. The state is composed of 10 life zones that extend from the prairies to the mountaintops. Numerous microscopic plants are also found in Idaho’s waterways and soils.
Idaho plants and shrubs are often unique to a certain type of geography. Sage brush is commonly found in arid regions. Plants that commonly grow in arid regions dominated by sage brush may include mountain snowberry, spineless horse-brush, prickly phlox, creeping Oregon grape, antelope bitterbrush, shrubby cinquefoil and others, notes Idaho State University. Arid regions with more alkaline soils typically have plants such as cat’s claw, greasewood and others. Woodland areas have plants such as mountain lover and willow. In riparian regions, Woods' rose, osier dogwood and some types of currants are found. Mountain meadows contain plants such as small-leaved laurels and willows.
The growing season in North and Central Idaho, which is mostly heavily forested and mountainous, is mainly short and rather cool, notes the University of Idaho. Southeast Idaho, which has desert in the west and high plains, has winters that are usually cold. The frost-free growing season in most of this area ranges from 30 to 150 days. Southwest Idaho, around Payette and Boise, is an excellent region for growing fruits and vegetables. Winters here are somewhat mild, allowing a long growing season of 120 to 150 days.
Idaho’s state flower is the Syringa (Philadelphus lewisii). This flower looks like an orange, so it’s also called Mock Orange. This is a deciduous shrub that produces four-petaled, cream-colored flowers. It grows best planted in well-drained soil, says Webreleaf.com. Prairie smoke, an indigenous mountain meadow plant, has red flowers that bloom in summer. Serviceberries, which are native shrubs, produce white flowers during spring and blue berries in summer. The munro globemallow has five-petaled, salmon-colored flowers and thrives in full sun, needing moderate watering. Monkeyflowers, which grow in mountain springs and streams, have large tubular flowers that are purplish-red.
Idaho’s state tree is the western white pine, which is found almost exclusively in the state’s Northern Rockies Eco-region. The western white pine was the most abundant type of forest tree until 50 years ago, notes IdahoForests.org. Other common Idaho trees include junipers, mountain mahoganies, ponderosas, pines and spruces.
Rush skeleton weed is an invasive plant that dislocates good forage plants, in addition to invading cheatgrass plant. This invasive plant grows throughout the intermountain west in the state. Spotted knapweed displaces native Idaho plants, increases plant erosion and lowers the value of forage. Leafy spurge plant is found in almost every county of Idaho and reduces forage value. The irritant latex of the plant causes blisters and even blindness, notes Defensive.org. Yellow starthistle takes over native plants and can poison horses.