Last updated October 1, 2009
| Name | Family | Nativity |
| Ranunculus sp. | Ranunculaceae | |
| Rauhia peruviana | Liliaceae | Peru |
| Rauvolfia caffra | Apocynaceae | South Africa |
| Rauvolfia samarensis | Apocynaceae | Philippines |
| Ravenea madagascariensis | Arecaceae | Madagascar |
| Ravenea monticola | Arecaceae | Madagascar |
| Ravenea rivularis | Arecaceae | Madagascar |
| Rebutia arenacea | Cactaceae | Bolivia(Cochabamba) |
| Rebutia canigueralii | Cactaceae | Bolivia |
| Rebutia peruviana | Cactaceae | |
| Reineckea carnea | Convallariaceae | China, Japan |
| Rhagodia spinescens v. deltophylla | Chenopodiaceae | S Australia |
| Rhamnus alaternus | Rhamnaceae | Portugal |
| Rhamnus californica cv. Eve Case | Rhamnaceae | California |
| Rhamnus californica cv. Eve Case | Rhamnaceae | Wester US |
| Rhamnus californicus | Rhamnaceae | W United States |
| Rhamnus californicus v. tomentella | Rhamnaceae | California |
| Rhaphidophora decursiva | Araceae | SE Asia |
| Rhapidophyllum hystrix | Arecaceae | SE United States |
| Rhapis excelsa | Arecaceae | S China |
| Rhapis humilis | Arecaceae | China |
| Rhipsalis cereuscula | Cactaceae | Cen Brazil to Uraguay |
| Rhipsalis cf. elliptica | Cactaceae | Brazil |
| Rhipsalis clavata | Cactaceae | SE Brazil |
| Rhipsalis crispa | Cactaceae | |
| Rhipsalis grandiflora | Cactaceae | Brazil |
| Rhipsalis micrantha | Cactaceae | Brazil |
| Rhipsalis micrantha | Cactaceae | Ecuador |
| Rhipsalis micrantha x naranja | Cactaceae | |
| Rhipsalis monacantha v. espinosa | Cactaceae | N Argentina |
| Rhipsalis pachyptera | Cactaceae | Brazil |
| Rhipsalis paradoxa | Cactaceae | Brazil |
| Rhipsalis paradoxa | Cactaceae | SE Brazil |
| Rhipsalis pentaptera | Cactaceae | S Brazil |
| Rhipsalis pilocarpa | Cactaceae | Brazil |
| Rhipsalis platycarpa | Cactaceae | Brazil |
| Rhipsalis rhombea | Cactaceae | Brazil |
| Rhipsalis sp. | Cactaceae | |
| Rhipsalis sulcata | Cactaceae | Brazil |
| Rhipsalis teres | Cactaceae | Brazil |
| Rhipsalis teres | Cactaceae | S Brazil |
| Rhododendron atlanticum | Ericaceae | North America |
| Rhododendron canescens | Ericaceae | North America |
| Rhododendron catawbiense x viscosum cv. Fragrans | Ericaceae | |
| Rhododendron cubittii cv. Ashcombe | Ericaceae | |
| Rhododendron cuffeanum | Ericaceae | |
| Rhododendron cv. Alaska | ericacaea | |
| Rhododendron cv. Anah Kruschke | Ericaceae | |
| Rhododendron cv. Angeles Crest | Ericaceae | |
| Rhododendron cv. Arthur Bedford | Ericaceae | |
| Rhododendron cv. Brilliant | ericacaea | |
| Rhododendron cv. Christmas Cheer | ericacaea | |
| Rhododendron cv. Chrysomanicum | Ericaceae | |
| Rhododendron cv. Corona | Ericaceae | |
| Rhododendron cv. Dame Nellie Melba | Ericaceae | |
| Rhododendron cv. Duc de Rohan | ericacaea | |
| Rhododendron cv. Fastuosum Flore Pleno | Ericaceae | |
| Rhododendron cv. Formosa | ericacaea | |
| Rhododendron cv. Forsterianum | Ericaceae | |
| Rhododendron cv. Fragrantissimum Improved | Ericaceae | |
| Rhododendron cv. George Budgen | Ericaceae | |
| Rhododendron cv. George Lindley Tabor | ericacaea | |
| Rhododendron cv. L. J. Bobbink | ericacaea | |
| Rhododendron cv. Loderi Ilam Cream | Ericaceae | |
| Rhododendron cv. Loder’s White | Ericaceae | |
| Rhododendron cv. Mamie | ericacaea | |
| Rhododendron cv. Mexicali Rose | ericacaea | |
| Rhododendron cv. My Mary | Ericaceae | |
| Rhododendron cv. Percy Wiseman | Ericaceae | |
| Rhododendron cv. Pink Pearl | Ericaceae | |
| Rhododendron cv. Point Defiance | Ericaceae | |
| Rhododendron cv. Pride of Dorking | ericacaea | |
| Rhododendron cv. Princess Alexandra | Ericaceae | |
| Rhododendron cv. Rainbow | Ericaceae | |
| Rhododendron cv. Red Wing | ericacaea | |
| Rhododendron cv. Reine Long | Ericaceae | |
| Rhododendron cv. Roseum Elegans | ericacaea | |
| Rhododendron cv. Southern Charm | ericacaea | |
| Rhododendron cv. Tahitian Dream | Ericaceae | |
| Rhododendron cv. Tressa McMurry | Ericaceae | |
| Rhododendron cv. Van Nes Sensation | Ericaceae | |
| Rhododendron cv. Warlock | Ericaceae | |
| Rhododendron cv. White Pearl | Ericaceae | |
| Rhododendron formosum | Ericaceae | India |
| Rhododendron ponticum | Ericaceae | Europe and Asia |
| Rhododendron sp. | Ericaceae | |
| Rhododendron viscosum x prunifolium | Ericaceae | |
| Rhododendron x atlanticum | Ericaceae | |
| Rhombophyllum dolabriforme | Aizoaceae | South Africa |
| Rhopalostylis baueri | Arecaceae | Australia(Norfolk Is.) |
| Rhopalostylis sapida | Arecaceae | New Zealand |
| Rhus integrifolia | Anacardiaceae | S California to Baja, Ca |
| Rhus lentii | Anacardiaceae | Mexico |
| Rhus ovata | Anacardiaceae | California |
| Rhynchospora colorata | Cyperaceae | SE United States |
| Ribes viburnifolium | Saxifragaceae | S California to NW Mexico |
| Rohdea japonica | Convallariaceae | China, Japan |
| Rosa cv. Cinco de Mayo | Rosaceae | |
| Rosa cv. Hot Cocoa | Rosaceae | |
| Rosa cv. Julia Child | Rosaceae | |
| Rosa cv. Livin’ Easy | Rosaceae | |
| Rosmarinus officinalis | Lamiaceae | Mediterranean |
| Rosmarinus officinalis cv. Lockwood de Forest | Lamiaceae | |
| Rosularia pallida | Crassulaceae | Cen Asia |
| Rotala indica | Lythraceae | Asia |
| Roystonea regia | Arecaceae | Cuba |
| Rudbeckia fulgida v. sullivantii cv. Goldstrum | Asteraceae | |
| Rudbeckia hirta | Asteraceae | E United States |
| Rudbeckia hirta cv. Cherokee Sunset | Asteraceae | |
| Ruellia brittoniana | Acanthaceae | Mexico |
| Ruellia macrantha | Acanthaceae | Brazil |
| Ruellia makoyana | Acanthaceae | Brazil |
| Ruellia sp. | Acanthaceae | |
| Rumohra adiantiformis | Polypodiaceae | Asia to Australia |
| Rumohra adiantiformis cv. Davis | Dryopteridaceae | |
| Ruschia centrocapsula | Aizoaceae | South Africa |
| Russelia equisetiformis | Scrophulariaceae | Mexico |
