Most plants that grow on the Pacific Northwest coast of the United States are adapted to high rainfall and acid soil. Areas in the rain shadow of the mountains are dry, with 20 inches of rain or less each year, but they still have the cool summers and mild winters that this area experiences. Different communities of plants colonize on shore edges, forest interiors, forest margins and open prairies.
Plants on the Pacific Northwest shore must survive in sandy soil or on rock outcroppings, with salty wind and even occasional splashes of sea water. Thick stems and deep taproots allow plants such as evening primrose, farewell-to-spring and coast buckwheat to grow in shifting sand. One of the most attractive flowers is the sea thrift, or Armeria maritima, which has small heads of pink flowers. It can be found on rocky shores across the northern hemisphere and in gardens worldwide.
Moss is present in all coastal ecosystems, but flourishes most abundantly in the shade of the tall conifers that are typical in the Pacific Northewest. Sitka spruce, red cedar, hemlock and Douglas fir are all substantial trees, growing several hundred feet tall or more. Ground covers include Vancouveria with tiny white flowers, western bleeding heart, yellow violets, sword fern and maidenhair fern. Understory shrubs and trees, such as vine maple, salal and osoberry, are an important part of the ecosystem.
At the edge of the forest, plants are sheltered by branches but get more sun than under the forest canopy. It is a transition zone, with a variety of microclimates that nourish a great diversity of plants. Wildflowers such as western columbine and Columbia lily thrive in the partial shade. Shrubs like Oregon grape, thimbleberry, beaked hazel and Nootka rose form thickets that provide shelter for a rich variety of wildlife.
Prairies and Meadows
Open prairies often have sandy or gravelly soil. Some were maintained by Native Americans by burning, to provide a home for the blue-purple flowered camas that was one of their staple foods. Prairies and meadows often support large stands of bracken fern and several kinds of lupine.
In the drier areas north and east of the Olympic mountains, madrona and Garry oak trees grow among the Douglas fir, and you'll find red-flowering currant blooming in early spring. Kinnikinnick is a common ground cover, and hairy manzanita grows as a shrub at the edge of the trees. Open meadows are more common here because of the lack of water, and they are thick with wildflowers in early spring.