I don’t immediately think about flowering plants when I think about the intertidal, particularly not on the exposed outer coast. In the rocky intertidal we are pretty much talking about surfgrass, Phyllospadix. Eelgrass, Zostera, washes up on the beaches all the time, especially near estuaries. I’m going to add diversity to this page by featuring other worthy flowering plants- ones that pioneer down onto the backshore, like dunegrass, Leymus mollis. Where dunes are absent, the willows, Salix, and a few others, sometimes creep down far enough to get an occasional salty soaking.
Unless otherwise mentioned in the caption, all the plants on this page are from the exposed northern Oregon coast. The organization and common names are my choice. I refer to the USDA PLANTS Database and the University and Jepson Herbaria for scientific names and distribution records. If you know a handy reference focusing on the Pacific Northwest, please let me know. I try to propose ID’s that are correct, but there’s always a chance of a mistake. Let me know if you see an error.
Eelgrass, Zostera marina– Eelgrass is at home in the bays and estuaries. It’s appearance on the surf-swept beaches is strictly in the drift line. Eelgrass was featured in Eelgrass in the Wrack and Beach Hoppers Rejoice Over Drift Macrophytes.
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Surfgrass, Phyllospadix– I think the one shown below is P. scouleri. It is at home on rocks, exposed by the lowest tides, and like eelgrass, it is sometimes prevalent in the drift line. Surfgrass was featured in Finding yourself in the Infralittoral Fringe and Comparative Photos Show Rocky Intertidal Changes Between 2013 and 2016.
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Dunegrass, Leymus mollis– Used to be the dominant grass on the dunes, but now it’s hard to find in the near-monoculture of Ammophila we find on the dunes. Wide grayish leaves set Elymus apart from Ammophila, which has narrow yellowish-green leaves. Leymus mollis is featured in Dunegrass Finds Breathing Room on the Backshore
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European beachgrass, Ammophila arenaria– Look for near-monocultures of Ammophila on almost any dune trail. Ammophila arenaria appears in Beachgrass Lights Up the Foredune and Stability and Change on the Foredune.
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Salal, Gaultheria shallon
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Dock, Rumex– Rumex are kind of a mystery to me. I’ve encountered some real beach pioneers, and this makes sense, most Rumex they have broad habitat tolerances. I’ve detected a couple on beach sand. They’re both shown below.
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Sea rocket, Cakile edentula– By summer, look for flowering sea rocket wherever there is a well developed backshore.
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Wild radish, Raphanus
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Honckenya peploides, sea purslane, seabeach sandwort
At the interface | Honckenya peploides walks a fine line as it creeps out of the forest onto beach sand 
Honckenya peploides forms an attractive mat
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Potentilla anserina, Pacific potentilla, silverweed
Potentilla anserina, foreground, can handle salt spray 
The forest above, the sea below | Potentilla anserina creeps out onto beach sand 
Potentilla anserina spreads with runners 
Potentilla anserina making a go of it in the highest wrack
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Sea-watch, Angelica lucida– Sea watch will get right down on the beach, especially where forested bluffs extend straight to the shore.
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Seaside Plantain, Plantago maritima
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A pioneering dandelion
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Coast mugwort, Artemisia suksdorfii
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Willow, Salix – I think this one is Hooker’s willow, S. hookeriana, also known as coastal or dune willow. Wherever the forest drops right down to the beach, especially where there are seeps, Salix can push down toward the intertidal as far as any forest plant – so low that they expose themselves to damage by winter’s high surf. Salix was featured in Sign of the Season.
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References
Kozloff, E. N. 1993. Seashore Life of the Northern Pacific Coast. 3rd ed. University of Washington Press.
Lamb, A. and B. P. Hanby. 2005. Marine Life of the Pacific Northwest. Harbour Publishing.
Pojar , J. and A. MacKinnon. 194. Plants of the Pacific Northwest Coast. Lone Pine Publishing.
Web Resources
