Although Rhododendrons had been known since the description of "Rhododendron hirsutum" by Charles de l'Écluse (Clusius) in the sixteenth century, and were known to classical writers (Magor 1990), and referred to as "Chamaerhododendron" (low-growing rose tree), the genus was first formally described by Linnaeus in his Species Plantarum in 1753. He listed five species under "Rhododendron" ("Rhododendron ferrugineum" (type species), "R. dauricum", "R. hirsutum", "R. chamaecistus" (now "Rhodothamnus chamaecistus" (L.) Rchb.) and "R. maximum"). At that time he considered the then known six species of "Azalea" that he had described earlier in 1735 in his Systema Naturae as a separate genus.