Rhododendron canescens Porter, Bull. Torrey Bot. Club. 16: 220 (1889), non R. canescens (Michx.) Sweet, Hort. Brit. ed. 2,343 (1830). Azalea prinophylla Small, N. Am. Fl. 29:42 (1914), nomen novum. Type: Pennsylvania, Monroe Co.: Pocono Summit. 22 v & 4 ix 1889, T. C. Porter s.n. (lecto., designated here, 22 v 1889, NY; isolecto. NY). Rhododendron roseum (Lois.) Rehder f. plenum Rehder, Contr. Gray Herb. 165: 10 (1947). Type: cultivated. Garden of R. H. P. Jacobus, originally found wild in the neighbouring woods. 23 vii 1935, R. H. P. Jacobus s.n. (holo. A). Rhododendron roseum (Lois.) Rehder f. albidum Steyerm., Rhodora 62: 131 (1960). Type: Missouri, Ste. Genevieve Co.: sandy pine-oak woods east of Chimney Rocks, along River Aux Vases, 5 mi E of Pickle. 24 v 1933, Steyermark 8522 (holo. MO; iso. MINN, MO)