While this is the largest-fruited species of the genus, and one of the most widely distributed, it is not the best in quality. From its native home in tropical America it has been carried to the eastern tropics, where it is now grown in many places. It is common in the West Indies, but nowhere is it cultivated on a commercial scale.
The plant is somewhat coarse and is a strong climber. The stems are four-angled, as indicated by the specific name, and the leaves are ovate or round-ovate, cordate at the base and mucronate at the apex, entire, and 6 or 8 inches long. The flowers, which are about 3 inches in diameter, are white and purple in color. The fruits are oblong, up to 10 inches in length. H. F. Macmillan says: "Its large, oblong, greenish-yellow fruit is not unlike a short and thick vegetable-marrow, and contains in its hollow center a mass of purple, sweet-acid pulp mixed with flat seeds." A horticultural form exists which has leaves variegated with yellow.
This species is more tropical in its requirements than P. ligularis and P. edulis. It will grow in southern Florida, but is not successful in California. A. Robertson-Proschowsky reports, however, that it has fruited on the French Riviera at Golfe-Juan and perhaps elsewhere, and in his own garden at Nice was only killed after surviving several winters.
Fig. 31. The giant granadilla (Passiflora quadrangularis). (X 1/4)
The fruit is known in French as barbadine, in Portuguese as maracuja melao, and in Spanish as granadilla or granadilla real. The name granadilla is applied, in different parts of the tropics, to several species of Passiflora, and in order to distinguish them it is necessary to append a qualifying word. It is derived from granada, and means "small pomegranate."
Macmillan recommends that the shoots be well cut back after the fruiting season is past. It is commonly believed necessary to resort to hand-pollination to insure the production of fruit, but this is not always the case. The protandrous character of the passifloras, and the necessity of cross-pollination, are mentioned in the discussion of the purple granadilla; that it is sometimes possible, however, for fruits to be produced by self-fertilization, has been shown by experience. Paul Knuth, after describing the character of the passiflora flower, says: "Autogamy (self-pollination) would seem to be excluded under such circumstances, yet it is possible that the stigmas and the anthers may be brought into contact when the flower closes at the end of the single day's anthesis. This is the more probable as Warnstorf saw a fully formed fruit in a greenhouse. Here, then, is a case in which an obviously chasmogamous flower (one in which the perianth opens) is only self-pollinated after it has closed." If P. quadrangularis is self-sterile, however, it would do no good to have the flowers self-pollinated. If insects are lacking to do the work, cross-pollination must be effected by hand.
Propagation is by seed or by cuttings, which should be 10 to 12 inches long and from well-matured stems, and should be inserted in sand.
Several other species of Passiflora are cultivated in the tropics for their fruit. P. laurifolia, known as yellow granadilla, water-lemon, Jamaica honeysuckle, sweet-cup, bell-apple, and pomme d'or, is cultivated in the West Indies, and to a limited extent in other regions. H. F. Macmillan states that it is not fruitful in the eastern tropics. P. maliformis, L. is grown in the West Indies, and in the mountains of Colombia, where it is called curuba or kuruba.