* Ramonda
* Ranunculus (buttercup, crowfoot)
* Ranzania
* Raoulia
* Raphia (raffia)
* Ratibida
* Ravenala (traveler's tree)
* Rebutia
* Rehderodendron
* Rehmannia
* Reineckia
* Reinwardtia
* Reseda (Mignonette)
* Retama
* Rhamnus
* Rhaphidophora
* Rhaphiolepis
* Rhapidophyllum (needle palm)
* Rhapis (lady palm)
* Rheum (rhubarb)
* Rhexiav
* Rhipsalis
* Rhodanthe (strawflower)
* Rhodanthemum
* Rhodiola
* Rhodochiton
* Rhododendron
* Rhodohypoxis
* Rhodophiala
* Rhodothamnus
* Rhodotypos
* Rhoeo
* Rhoicissus
* Rhombophyllum
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* Rhus (sumac)
* Rhynchelytrum
* Rhynchostylis (an orchid genus)
* Ribes (currant)
* Richea
* Ricinus (castor-oil plant)
* Rigidella
* Robinia
* Rochea
* Rodgersia
* Rodriguezia
* Rohdea
* Romanzoffia
* Romneya (Matilija poppy, tree poppy)
* Romulea
* Rondeletia
* Rosa (rose)
* Roscoea
* Rosmarinus (rosemary)
* Rossioglossum
* Rothmannia
* Roystonea (royal palm)
* Rubus (raspberry)
* Rudbeckia (coneflower)
* Ruellia
* Rumex (dock)
* Rumohra
* Rupicapnos
* Ruschia
* Ruscus
* Russelia
* Ruta (rue)
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