Hunting for Rhododendron macrophyllum in Skamania County, Washington.
In the Mount Hood region of the northern Oregon Cascades the Pacific Rhododendron (R macrophyllum) commonly forms impenetrable thickets, and scattered plants, in the understory of mixed conifer forests. I have gone on hikes in Skamania County, especially at Siouxon Creek and around Mt St Helens, and do not recall having seen it growing there. I have been finding R menziesii and R albiflorum however. R menziesii, which I was not familiar with until earlier this year is fairly widespread, while R albiflorum is present about 3,900' elevation on the west side of Mt St Helens in suitable habitat in Cowlitz County, east of Elk Pass, and in Indian Heaven Wilderness along the Thomas Lake Trail. I had heard that R macrophyllum was found in the vicinity of Big Huckleberry Mountain. On an early winter hike along the Pacific Crest Trail south of BHM we failed to find it, but then a late start, and early sunset curtailed getting to the area where they are found.
A search of the Consortium of Pacific Northwest Herbaria website yielded three specimens from Skamania County. Two collected by Wilhelm Suksdorf in 1896 along Moss Creek, and a more recent speciment collected in July 1965 by James R Slater west of the "Hemlock Rager Station." This is believed to be the Wind River Ranger station. see: http://www.pnwherbaria.org/data/results.php?DisplayAs=WebPage&ExcludeCultivated=Y&GroupBy=ungrouped&SortBy=Year&SortOrder=DESC&SearchAllHerbaria=Y&QueryCount=1&IncludeSynonyms1=Y&Genus1=rhododendron%20&Species1=macrophyllum&County1=skamania&Zoom=4&Lat=55&Lng=-135&PolygonCount=0
Question is, why is R macrophyllum so uncommon on the north side of the Columbia River when it is so common on the south side? One factor could be the 1902 Yacolt Burn which burnt 90,000 acres of Skamania and Clark Counties. And who knows, it just might be common in areas I haven't yet spent much time in.