Plants in the state of Oregon vary according to geography, which greatly affects the rainfall and amount of sunshine available to plants. Meriwether Lewis and William Clark first documented the state's native plant life when their expedition passed along the Columbia River, Oregon's northern border with Washington state in 1805.
Georgraphy and Plant Life
The Oregon coast is flanked by low mountains. The narrow strip between the mountains and the cliff-lined ocean receives the heaviest rainfall in the state and a cloud cover most of the year. The rain comes from prevailing marine winds blowing off the Pacific Ocean. This area contains rhododendrons, Oregon grape, Scotch bloom and other shrubs that can take heavy rainfall.
The Willamette River Valley--located between the between the Coast Range and the higher Cascade Range of mountains--is an agricultural area with grass seed being produced near Eugene. Numerous vineyards and hazel nut orchards are located at the northern end close to Portland. Pears are grown at the southern end near Medford.
Willamette Valley and Coastal Trees
The Coast Range and the Cascade Mountains are heavily forested with Douglas fir, the state tree, spruce and hemlock. This area also contains maple, ash, oak and willow trees.
Columbia Plateau Trees
Western juniper trees are found throughout the Columbia Plateau. Lodgepole, Tamarack, sugar and Ponderosa pines are found in the Blue Mountains and the Wallowa Mountains.
Columbia Plateau Plants
The semi-arid desert that covers much of eastern Oregon includes purple sagebrush, big sagebrush, small prickly pear cacti, milk vetch, bluebells, brodiaea and phlox.
Willamette Valley and Coastal Plants
The plants in the Willamette Valley and the Oregon coast were first documented by the Lewis and Clark Expedition. In September 1805, having reached the rapids near present day The Dalles, he recorded the Oregon grape and vine maple. Upon reaching the Pacific Ocean, he recorded the madrona, white alder, Oregon boxwood, Oregon ash and California rhododendron.
In 1806, camped near the mouth of the Columbia, he noted salal, huckleberry, elderberry, Oregon crabapple, straggly gooseberry, flowering currant, salmonberry, bigleaf maple, balsam, root, larkspur, service berry, pestle parsnip, sagebrush, wild hyacinth and ocean spray. On his return he recorded black hawthorne, phlox, daisies, western wallflowers giant rye grass and cottonwood trees.