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