NPSO PDX, Native Rhododendrons of Oregon's Boletim

Although we are well past the peak of hybrid rhododendron blooming period there are still some that are late bloomers. And there are some that will get reported as our native "Rhododendron macrophyllum" on iNaturalist.

Things to consider when reporting rhododendrons on iNaturalist. Rhododendrons did not evolve in savannas or deserts and are not found in those habitats. Rhododendrons are a very popular garden plant and there are many many hybrids, and cultivars, on the market. Rhododendrons found in private gardens are not wild, or species rhododendrons. Rhododendrons in public, and botanic, gardens are not wild. Rhododendrons found in wild urban parks may not be wild, such as Forest Park, Portland, OR and Sequoia Park, Eureka, CA, are not wild plants. A rule of thumb is that any rhododendron in an urban setting is probably not going to be wild, and possibly not Rhododendron macrophyllum.
Rhododendron macrophyllum has been used as a parent plant with some hybridizers, but it is not widely used, and most commercially available hybrids don't have it as a parent. It is sometimes sold in Native Plant section of nurseries, but it is not easily grown in the summer dry and warm lowlands surrounding the Willamette Valley, or Rogue Valley around Ashland/Medford.
It's in a name! Macrophyllum simply means big leaf. Macro = big, phyllum = leaf; and phyllum is pronounced: fill-um, not fy-lum.
There are a few extremes in coloring, but R. macrophyllum flowers tend to be pale pink and the pistil is a dark pink; the spots on the upper portion of the flower are also generally a bronzy color. There are variations. I have an album on flickr that shows some of the R. macrophyllum flowers I have photographed. More continue to be added. It can be seen thru this link: https://www.flickr.com/photos/ujelang/albums/72177720299414513
Enjoy the photos, but they may not be used without prior permission. And enjoy looking for, and finding, Oregon's wild native rhododendrons, there are five of them: R. albiflorum, columbianum, macrophyllum, and menziesii, . And don't forget to add them to iNaturalist.

Currently (26 Jun 2023) on iNaturalist there is only one record of R. albiflorum south, or west, of Hwy 22 in the Oregon Cascades. That record is from Bugaboo Ridge, Bachelor Mountain. There are currently no observations on iNaturalist south of Hwy 20. According to the Consortium of Pacific Northwest Herbaria (CPNWH) (pnwherbaria.org) Roy C Andrews collected this species on Indian Ridge, Lane County in 1935 and 1938. Other than a specimen from Bachelor Butte made in 1926 by E. Anderson those two records are the furthest south records of R. albiflorum in the Oregon Cascades.

I hope hikers will keep their eyes out for R. albiflorum south of Hwy 20 in the Oregon Cascades. The plants will probably be growing in somewhat damp areas well above 4,000' elevation, along rocky ridge lines, or near streams, lakes and meadow edges, possibly hiding in plain sight with Vaccinium spp.

In North-east Oregon they are currently known only from the Elkhorn Mountains, but not in the Wallowas, which seems odd since R. columbianum (formerly Ledum glandulosum) is found in the Wallowas, but not the Elkhorns. R. menziesii is apparently not found in either the Elkhorns, or the Wallowas since there are no records of this species on either iNaturalist, or in the CPNWH database from either of those locations. It is however found fairly close by in Idaho. Keep your eyes open!