The coast line alternates between rocky headlands and long sandy beaches, dissected by a few rivers and estuaries with rocky to sandy or marshy shorelines. A few species of vascular plants are adapted to this saline environment, and are found throughout the area.

Salt Water Plant Communities
Rocky Ocean Shores are dramatic, jutting out into the ocean, enduring waves, salt spray and strong winds. One flowering plant, Scouler's surfgrass, is found in rocky intertidal pools along the ocean along with several dozen species of macroalgae. Above tidelines, salt spray zone plants include maritime plantain, red fescue and bluegrass, growing just below sea cliff meadows, see below in grasslands.

Sandy Beaches are common along most of the coast. Sea rocket, silver bursage, large-headed sedge, honkenya, yellow sand verbena and beach carrot grow in open sand between vegetated dunes and high tide.

Salt marsh species include tufted hairgrass, salt grass, pickleweed, jaumea, glaux, arrowgrass, northern starwort, gumweed, Lyngby's sedge and Baltic rush. In more brackish areas, springbank clover, Pacific silverweed, angelica and Douglas's aster are common, along with sedges, bulrushes, and rushes. Marshes grow in close relationship to mean tidal heights, and are generally found within two feet of mean higher high water, growing over a range of about three to four feet. A slow transition from salt to fresh species is common in these marshes, with salt-tolerant species near the lower edge, and salt-intolerant species near the upper or near freshwater sources.

Saltwater Tidal Flats are common habitats along the Columbia Coast. Both salt and freshwater tidal areas can be readily visited. In highly saline tidal flats below marshes, two eelgrasses are found, Zostera marina and Z. japonica. A non-native grass, smooth cordgrass, is presently colonizing eelgrass flats and growing into native salt marshes in Willapa Bay and Grays Harbor, displacing clams, eelgrasses, and feeding habitat for shorebirds, ducks, fish and other species. Three square bulrush grows in distinctive open patches. Dense tall stands of hardstem bulrush grow in brackish quiet waters. Cattails are found at the salt-fresh boundary, broadleaf cattail and narrowleaf cattail.

Fresh Water Communities
Freshwater tidal marshes are often dominated by non-native plants, such as purple loosestrife and reed canary grass. These habitats have been highly disturbed by diking, draining and dredge materials disposal; intact communities are rare. Particularly along the Columbia River, non-native plants are widely dispersed in water by farming and shipping activities. In the absence of disturbance, sneezeweed, wapato, frog-bit, several rushes and sedges are common.

Freshwater tidal flats are particularly extensive along the Columbia River. Like the marshes, these areas have been significantly impacted by dredging, and dredge materials dumping.