While Taisha was helping with the BC Butterfly Atlas workshop last weekend, I was attending the annual meeting of the Native Plant Society of Oregon. I had the privilege of being on a field trip that had special access to private property surrounding Angora Peak. We observed several state-sensitive / rare / locally-endemic plant species, including Filipendula occidentalis. Other biological treasures in the area included salamanders, long-tailed frogs (didn't get to see the one we encountered before it hid) and petaltail dragonflies (too early in the season to see).
This member of the rose family is only known from Washington's Pacific County and Oregon's Clatsop, Tillamook, Lincoln and Polk counties (and maybe Hood River, seemingly). It is one of two Filipendula species native to North America; the other is Filipendula rubra, commonly known as queen of the prairie. Filipendula occidentalis has a similar common name, queen of the forest. It's a bit of a misnomer, as the species is more associated with either bedrock crevices with near-permanent water seeps or the high-water mark of rocky-shored rivers rather than forest proper. I suppose queen of the seeps isn't acceptable.
The third photograph shows the habitat, as well as some look-alikes from a distance. The angular pipe-brush-like inflorescences of Aruncus dioicus are quickly distinguishable from the Filipendula, but at the distance this photograph was taken, the flowering heads of Heracleum maximum mask the Filipendula exceptionally well (hint: the Filipendula occidentalis is the lowermost cluster of white flowers). We were extremely fortunate to see any plants in flower, as they typically flower in late June / early July in this locale. I was only expecting to see foliage, so the flowers were one of two botanical highlights of the trip.