Passiflora quadrangularis
— Navneord
– Engelsk
～ tropical American passionflower yielding the large granadilla fruit
Paris quadrifolia
— Navneord
– Engelsk
～ European herb with yellow-green flowers resembling and closely related to the trilliums; reputed to be poisonous
Pinus quadrifolia
— Navneord
– Engelsk
～ five-needled pinon of southern California and northern Baja California having (sometimes three-needled or four-needled showing hybridization from Pinus californiarum)