Passiflora
Sp. Pl. 2: 955. 1753.
Gen. Pl. ed. 5, 410. 1754.
Vines, glabrous or densely hairy, sometimes glandular. Stems terete to angled; tendrils simple [branched]. Leaves petiolate; stipules leaflike to minutely setaceous, margins entire, serrate, or deeply cleft, sometimes glandular; blade (2)3(–9)-lobed or unlobed, base cuneate to cordate or rarely peltate, surfaces sometimes glandular, glands or nectaries associated with marginal teeth or abaxially near margins or between primary veins. Inflorescences solitary or paired flowers, simple or many-branched [pedunculate cyme with central pedicel often as aborted tendril], secondary inflorescences sometimes present as condensed, axillary (terminal) shoots; bracts 0 or (1–)3, scattered to whorled, margins sometimes glandular. Flowers bisexual or sometimes functionally unisexual [staminate]; hypanthium flattened to cuplike or tubular; sepals sometimes with subapical setose to leaflike projection; stamens 5[8], usually alternate with petals, borne on short to elongate androgynophore; anthers dorsifixed, versatile; ovary 3[–5]-carpellate, borne at tip of androgynophore. Fruits baccate [capsular or capsulelike berries]. x = 6.
Distribution
North America, Mexico, Central America, West Indies, South America, Australasia, warm-temperate to tropical areas, some species introduced in the tropics worldwide.
Discussion
Species ca. 550 (18 in the flora).
Passiflora species have been arranged under a variety of infrageneric systems, with the 22 subgeneric system by E. P. Killip (1938) the most commonly used until recently. The most recent system (C. Feuillet and J. M. MacDougal 2003) recognizes only four subgenera: Astrophea (de Candolle) Masters, Decaloba (de Candolle) Reichenbach, Deidamioides (Harms) Killip, and Passiflora. The flora area includes species of only the two largest subgenera: Passiflora, with relatively large flowers and fruits and a predominant chromosome number of n = 9, and Decaloba, with relatively small flowers and fruits and a predominant chromosome number of n = 6. Recent molecular-based phylogenetic studies have investigated the relationships and circumscriptions of infrageneric groups, generally supporting the Feuillet and MacDougal subgeneric classification (for example, V. C. Muschner et al. 2003; R. Yockteng and S. Nadot 2004; A. K. Hansen et al. 2006; S. E. Krosnick et al. 2013).
Primarily outcrossers, Passiflora flowers attract pollinators by fragrance, showiness, or nectar secreted within the hypanthium. While collecting nectar, visitors inadvertently collect downward when receptive, then erect again when no longer receptive. Passiflora species are pollinated principally by insects (generally flying Hymenoptera), which seem to prefer scented species. However, species with long-tubular, scentless, red flowers (especially common in the Andes) are hummingbird-pollinated, and bat pollination is also known (T. Ulmer and J. M. MacDougal 2004). Our native species have a conspicuous corona, are scented, and are insect-pollinated. Passiflora incarnata is pollinated primarily by carpenter bees (Hymenoptera, Anthophoridae; C. M. McGuire 1999). Passiflora lutea is pollinated by various hymenoptera, including wasps (J. M. MacDougal 1983), and a ground-nesting bee, Anthemurgus passiflorae (Hymenoptera, Andrenidae), that pollinates only this species of Passiflora (and no other plant species) and with which it shares a similar geographic distribution (C. D. Michener et al. 1994; J. L. Neff and J. G. Rozen 1995; Neff 2003).
Passiflora fruits are generally adapted to animal consumption for seed dispersal. The relatively large, fragrant, and often yellowish fruits of subgenus Passiflora are probably mammal-dispersed; the relatively small, often purplish berries with occasionally brightly colored arils of subgenus Decaloba are probably bird-dispersed (J. M. MacDougal 1983).
Some butterflies of the family Nymphalidae (Nymphalinae, Heliconiinae) are obligate-associates of Passiflora, using plants as larval hosts (L. E. Gilbert 1982). The larvae sequester and metabolize plant toxins for their own defense against predation, even into adulthood, which has resulted in complicated Batesian and Muellerian mimicry networks of Heliconiinae species. Passiflora-Heliconiinae coevolution has been a subject of interest (W. W. Benson et al. 1975). Passiflora defenses include extreme leaf polymorphism (Benson et al.), defensive trichomes (Gilbert; J. M. MacDougal 1994), extrafloral nectaries (Benson et al.), and butterfly egg-mimicry (Gilbert; K. S. Williams and Gilbert 1981). Some Passiflora species exhibit polymorphism is best exemplified in the closely related P. pallida and P. tenuiloba; color variation is most strongly expressed in P. mexicana and P. pallens. Extrafloral nectaries occur most commonly on petioles, stipules, leaf margins and abaxial surfaces, and floral bracts, attracting potential defenders such as predatory or parasitic Hymenoptera; see J. A. Scott (1986) for a survey of Heliconiinae associated with Passiflora in North America.
Fifteenth-century Spanish explorers were the first Europeans to encounter Passiflora. Some saw religious symbolism in its floral morphology, signifying various aspects of Christ’s crucifixion (E. E. Kugler and L. A. King 2004), the three styles representing the nails, the corona representing the crown of thorns, and red coloration (if present) representing the blood of Christ. This symbolism led to its cultivation in Europe in the early seventeenth century; P. incarnata was probably the first species grown there.
Several species are cultivated for their edible fruits, including Passiflora edulis Sims, P. laurifolia Linnaeus, P. quadrangularis Linnaeus, P. tarminiana, P. tripartita (Jussieu) Poiret var. mollissima (Kunth) Holm-Nielsen & P. Jørgensen, and P. vitifolia Kunth (T. Ulmer and J. M. MacDougal 2004). However, because the genus is generally cyanogenic, immature fruits of all species are probably poisonous and should not be consumed.
Although Passiflora is commonly considered tropical, the flora area has several native cold-tolerant species. Many of these invest heavily in below-ground structures, having rhizomes or root-suckers (for example, P. affinis, P. filipes, P. foetida var. gossypiifolia, P. incarnata, P. lutea, P. mexicana, and P. tenuiloba).
Passiflora species are horticulturally desirable because of the unusual appearance and attractiveness of their flowers and leaves. Because of their popularity, it is expected that the number of species naturalized in the flora area will increase. In our flora, P. arida, P. caerulea, and P. tarminiana are well-established escapes that are also popular in horticulture. However, there are currently far fewer species of Passiflora introduced and established in our range than have been reported (J. T. Kartesz 1994), some cultivated only (D. G. Burch et al. 1988). Species long-persisting in old plantings, “naturalizing” merely by root-suckering, or historical adventives that are long-absent or poorly documented, are not formally covered in this treatment, for example, P. ×belotii Pepin (P. alata Curtis × P. caerulea; R. P. Wunderlin and B. F. Hansen 2003), P. edulis (Wunderlin and Hansen), P. gracilis (E. P. Killip 1938), P. ‘Incense’ (P. incarnata × P. cincinnata), P. manicata (C. F. Smith 1976), P. miniata (Wunderlin and Hansen, identified as P. coccinea), P. mixta Linnaeus, and P. morifolia Masters (Killip; A. E. Radford et al. 1968; syn. P. warmingii). Passiflora ×belotii does not form fruit and it is unlikely to naturalize except by rooting at the nodes of fallen branches or possibly by suckering. J. C. Estill and M. B. Cruzan (2001) mentioned that P. morifolia is endemic to South Carolina, whereas it is actually native only to Central and South America. Currently, any minimally “naturalized” species or hybrids listed above that might be encountered are in California or Florida, specifically P. ×belotii, P. edulis, and P. ‘Incense’, P. miniata, and P. mixta. In the key below, P. ×belotii will key to P. caerulea, P. edulis and P. ‘Incense’ to P. incarnata, P. miniata to P. multiflora, and P. mixta to P. tarminiana. For broad and well-illustrated treatments of the genus, see T. Ulmer and J. M. MacDougal (2004), and J. Vanderplank (2000).
Selected References
Lower Taxa
Key
| 1 | Primary leaf lobes 2 or 3, often appearing 2-lobed (middle lobe absent), middle lobe much shorter than lateral lobes, usually symmetric, or strongly asymmetrically 2- or 3-lobed with 1 lateral lobe greatly reduced or absent | > 2 |
| 1 | Primary leaf lobes 3+, or 0, not appearing 2-lobed, middle primary lobe ± as long as or longer than lateral 2 primary lobes, blade usually symmetric | > 6 |
| 2 | Leaf blades strongly asymmetric and 2- or 3-lobed, with 1 of the 2 primary lateral lobes greatly reduced or absent | Passiflora pallida |
| 2 | Leaf blades roughly symmetric, 2- or 3-lobed, both primary lateral lobes present | > 3 |
| 3 | Leaf blades with conspicuous nectaries on abaxial surface, usually forming lines; sepals 13–17 mm | > 4 |
| 3 | Leaf blades without conspicuous nectaries on abaxial surface, or if present, not forming lines and always near leaf margins; sepals 6–13 mm | > 5 |
| 4 | Stems minutely puberulent; abaxial leaf nectaries usually in lines extending to leaf lobes, at least on flowering stems; fine leaf veins prominently raised abaxially; corona filaments laterally flattened, green basally, yellow apically; se Florida. | Passiflora biflora |
| 4 | Stems glabrous; abaxial leaf nectaries in lines rarely extending to leaf lobes, at least on flowering stems; fine leaf veins weakly to moderately raised abaxially; corona filaments terete, red, becoming purple; Arizona. | Passiflora mexicana |
| 5 | Leaf blades densely soft-hairy, lobes unlobed, abaxial nectaries absent; petioles eglandular; se Florida. | Passiflora sexflora |
| 5 | Leaf blades glabrous or subglabrous to short-hairy, not soft-hairy, primary 3 lobes often lobed, abaxial nectaries present or absent; petioles with cuplike glands; Texas. | Passiflora tenuiloba |
| 6 | Stipules pectinate, with usually prominent gland-tipped hairs or bristles; leaves often pungent; floral bracts pinnatifid, often with glandular bristles or hairs | > 7 |
| 6 | Stipules not pectinate, glabrous or hairy but without gland-tipped bristles or hairs; leaves usually not pungent; floral bracts absent, or present and not pinnatifid but with margins entire or serrate, dentate, or erose, eglandular to sessile-glandular | > 10 |
| 7 | Plants densely woolly-hairy; stipules, blades, and floral bracts with obscurely glandular to eglandular bristles or hairs; leaf blades deeply (3–)5–7(–9)-lobed. | Passiflora arida |
| 7 | Plants glabrous or hairy but not densely woolly; stipules, blades, and floral bracts with obvious gland-tipped bristles or hairs; leaf blades moderately to deeply 3(–5)-lobed | > 8 |
| 8 | Leaf margins sharply dentate; Arizona | Passiflora arizonica |
| 8 | Leaf margins serrate to nearly entire; Florida, Texas | > 9 |
| 9 | Fruits bright red to crimson; leaves not or weakly pungent, glabrous or hairy, blade 3–10(–12) × 3–8(–10) cm; Florida, Texas. | Passiflora ciliata |
| 9 | Fruits green to yellow-green; leaves pungent, densely hairy, blade 3–5(–8) × 2.5–5.5(–7) cm; Texas. | Passiflora foetida |
| 10 | Leaves soft-hairy abaxially | > 11 |
| 10 | Leaves glabrous or hairy to hispid abaxially, but not soft-hairy | > 12 |
| 11 | Leaf blades deeply 3-lobed, margins serrate; stipules subreniform, often leaflike, 2–3 mm wide; petals 40–54 mm, floral tube 60–80 mm | > 11 |
| 11 | Leaf blades unlobed to rarely obscurely 3–5-lobed, margins entire; stipules linear-setaceous, 0.5 mm wide; petals 4–5 mm, floral tube absent. | Passiflora multiflora |
| 12 | Petioles eglandular | > 13 |
| 12 | Petioles glandular | > 15 |
| 13 | Leaf blades with abaxial nectaries; floral bracts 1–3 mm; sepals 10–16 mm, outer corona filaments apically clavate; c Texas. | Passiflora affinis |
| 13 | Leaf blades without abaxial nectaries; floral bracts absent; sepals 6–10 mm, outer corona filaments not apically clavate; s Texas or widespread | > 14 |
| 14 | Fine veins on abaxial leaf surface raised (especially in dried specimens), leaf blade 2–10(–15) cm, middle lobe usually 1/3–2/3 blade length; widespread (excluding southernmost Texas). | Passiflora lutea |
| 14 | Fine veins on abaxial leaf surface not raised, leaf blade 1–3(–5) cm, middle lobe usually to 1/4 blade length; southernmost Texas. | Passiflora filipes |
| 15 | Stems and leaves uncinate-hairy. | Passiflora bryonioides |
| 16 | Stipules linear-subulate or linear-setaceous, 0.5–1 mm wide | > 18 |
| 17 | Leaf blades shallowly 3-lobed; young stems terete; Florida. | Passiflora pallens |
| 17 | Leaf blades deeply 3–9-lobed; young stems angular; California. | Passiflora caerulea |
| 18 | Leaf blades 3(–5)-lobed, margins serrate; sepals 20–30 mm, petals 25–35 mm; fruits 30–60 mm, green to pale yellow; bark not corky. | Passiflora incarnata |
| 18 | Leaf blades unlobed or 3–9-lobed, margins entire; sepals 4–10 mm, petals absent; fruits 5–13 mm, dark blue to black; bark corky or not | > 19 |
| 19 | Bark not corky; leaf blades as wide as to usually wider than long, 3–9-lobed, lobes acute, abaxial nectaries present or absent, petiole glands cuplike; Texas. | Passiflora tenuiloba |
| 19 | Bark with corky ridges or wings; leaf blades as long as to usually longer than wide, unlobed or 3-lobed, lobes rounded to acute, abaxial nectaries absent, petiole glands clavate; Florida, Texas. | Passiflora pallida |