- protophyte
- prunella
- psammophyte
- pseudaxis
- pseudoangiocarpic
- pseudobuld
- pseudosperm
- puccoon
- puff-ball
- pulp
- pulvinus
- pussy
- put-up
- pycnid
- pyxides
- pyxis
- punicaceae
- purebred
- purslane
- putamina
- pycnidium
- pyrene
- pyrethrum
- pyxidia
- quadricapsular
- quadrilobate
- quadriphyllous
- punctate
- puncticulate
- punica
- pussy-willow
- putamen
- pycnial
- quadricarpellary
- quadrifid
- quadripinnate
- quassia
- pyxidium
- quinate
- quince
- quinquefarious
- quinquefid
- quinquevalve
- quill-wort
- quinque-dentate
- quinquefoliate
- quitch
- raceme
- racemiferous
- racemose
- racemule
- racemulose
- rachilla
- rachis
- radiant
- radiate-veined
- radical
- radiciform
- radicle
- raffia
- ragwort
- radish
- radius
- ragweed
- ramal
- rambler
- rament
- ramule
- rape
- raphia
- rattan
- rambutan
- ramee
- ramellose
- ramie
- ramiform
- raspberry
- ratan
- ray
- ramiferous
- ramiflorous
- ramoconidium
- rampion
- ranunculaceae
- raphe
- raspberry-cane
- rattle
- receptacle
- reclinate
- recti-nerved
- red-root
- recurved
- red-seeded
- reduplicate
- reed
- rennet
- reindeermoss
- replum
- reseda
- resting