Passiflora edulis
(passionfruit)

P. edulis is less frequently regarded as a serious invasive when compared with the related species P.mollissima or P. foetida. However it has the ability to spread and dominate large areas in tropical and subtropical mesic to wet environments – especially areas in disturbed forest and scrub, including forests edges, gaps and riparian zones. The species may be allelopathic and as a climbing spreading vine it can become dominant in both the canopy and understory, where its weighty vines can weigh down and shade co-occurring trees, shrubs and herbs. P. edulis is listed as invasive in the Galapagos, Hawaii, Raoul and other tropical oceanic islands. It is naturalized and spreading but usually regarded as a minor weed in most areas where it is introduced e.g. Australia and Africa. As with many weedy crop species its invasiveness may be under-reported because of its useful qualities.

P. edulis is native to South America, from Brazil through Paraguay and northern Argentina. It is generally not reported as native to northern South America, though in some accounts it is listed as native in Venezuela and Colombia (Cervi, 1997). It is widely cultivated in tropical Africa, South-East Asia and tropical America and the Caribbean (Francis, 2000; PROTA, 2014; USDA-ARS, 2014). 

This plant will continue spreading into new locations, initially because of its desirable qualities as a food and ornamental plant. The fruit will be transported for consumption (this could create an opportunity for accidental spread) and the seeds for planting. The plant can also be propagated readily from cuttings. Once a plant is established in a location, livestock, tortoises, monkeys, primates and birds can eat the fruit and potentially will spread the seeds, which remain viable after ingestion in many cases. Also, within areas where it is grown, dumping of garden waste could lead to accidental introduction to new sites.

P. edulis grows in tropical and subtropical mesic to wet environments – especially forests and scrub, forest edges, forest gaps and riparian areas in forests. It probably benefits from supporting woody vegetation or uneven terrain, since its tendrils and vining or scrambling habit allow it to grow up and over its surroundings to capture resources.

The weediness and impacts of P. edulis are features of its fast growth and climbing and smothering habit and dispersal ability, although long distance dispersal may be rare. It may by virtue of proximity affect any plant upon which it grows, climbing upwards in the canopy supported by twining vines with tendrils that grasp nearby supporting vegetation or other items that provide structural support. In forested situations this might mean growth into the canopy. This may actually be a requirement for its reproduction, since fruit are unlikely to be produced in full shade. So far, concerns about the invasiveness of this species are generally in the context of it being a weed of forests, forest gaps and forest margins – especially in sites with high biodiversity value (Holt, 1992; West, 2002). For example the rare Scalesia pedunculata forests in the Galapagos islands are severely infested and of high value (Rentería and Buddenhagen, 2006). Its productivity in cultivation may be indicative of its capacity for spread, with 15-20 tons per hectare per year being possible (Bautista and Salas, 1995).

Genetics

The chromosome number reported for P. edulis is 2n =18 (Melo et al., 2001; Hansen et al., 2006). The genetic diversity of the group has been investigated and shows no useful distinction between the varieties based on fruit colour (Santos et al., 2011).

Reproductive Biology

Flowers open shortly after sunrise and remain open until mid-morning the next day, but the stigma is receptive only on the first day. The purple passion-fruit is self-compatible, setting well if selfed, but the yellow passion-fruit often requires cross-pollination (Bruckner et al., 1993). Bumblebees (Xylocopa spp.; Bombus spp. and others) are the main bees that pollinate the flowers of the passion fruit; when and where they are not sufficiently active, hand pollination can be practised where the plant is cultivated. Flower buds emerge sequentially on the new shoots. They take 40-46 days to anthesis; the purple fruit matures 60-90 days later, the yellow fruit after 60-70 days.

Physiology and phenology

In Puerto Rico, P. edulis has been recorded flowering from April to October and fruiting from June to December (Acevedo-Rodríguez, 2005). In China, it flowers in June and fruits in November.

Growth and Development

As in many vines, light is the essential factor for flowering and in passion-fruit this is particularly true for floral development and fruit set. That is why training and pruning are important to ensure adequate exposure of the shoots when grown as a crop. In a monsoon climate most flowers are produced on the flush occurring at the end of the rainy season. Depending on the climate there may be one to three harvest peaks (purple passion-fruit) or a single, often very long harvest season (more common with the yellow passion-fruit).

Seeds lose their viability within a few weeks. Germination takes 2-4 weeks; the seedlings grow slowly and require 3-4 months to reach the transplanting height of 20-25 cm. Within 5-7 weeks after transplanting, each plant will have up to four healthy laterals. From then on the vine grows very rapidly; the first flowers are produced 5-7 months after transplanting when the vine can be 10-15 m long.

Environmental Requirements

The yellow passion-fruit grows best at altitudes of 0-800 m; the purple passion-fruit forms virtually no flowers below 1000 m and should be grown commercially at altitudes of 1200-2000 m.

The purple-flowered form tolerates light frosts and can be grown in the subtropics, as in Australia and New Zealand, while the yellow fruited variety is not, or is less tolerant of frost. Both crops grow on a wide range of soils; heavy clay soils have to be drained and very sandy ones need heavy manuring. A pH of 6-8 is preferred. In South-East Asia, it grown in areas with 2000-3000 mm annual rainfall, but the purple passion-fruit, especially, grows well on as little as 900 mm in Africa and Australia, provided the rainfall is well distributed.

The vines require sheltered locations without extreme temperatures: below 20°C pollen does not germinate and at 18-15°C both growth and flowering are set back, whereas temperatures above 30-32°C stimulate growth at the expense of flowering and fruit set. These critical temperatures were established for hybrid cultivars in Australia (Martin and Nakasone, 1970).

Caterpillars of the Andean Silverspot (Dione glycera), the Juno Silverspot (Dione juno ), and the Gulf Fritillary (Agraulis vanillae)  have been recorded in Venezuela (2070-3170 m alt.) feeding on P. edulis and causing serious foliage damage; in some cases adults oviposited on the plant (Causton et al., 2000). Also in Venezuela at 1200–2680 m altitude adult beetles of Lactica brevicollis have been recorded to feed on foliage and flowers, and the larvae to feed on roots of P. edulis, but  neither the beetles nor the butterflies identified in the study were specialists on P. edulis (Causton et al., 2000). This study focused on identifying natural enemies of the more invasive Passiflora mollisima, and identified a number of other polyphagous insects that presumably feed on this focal species and some others but it was not clear if they feed on P. edulis (Causton et al., 2000).

Fruit fly larvae Dasiops gracilis are known from immature fruit in Venezuela and Dasiops inedulis and Dasiops curubae larvae feed on immature flowers in Brazil, Ecuador, Bolivia and Venezuela (Aguiar-Menezes et al., 2004, Friesen et al., 2008). Spider mites Eutetranychus banksi and Mononychellus tanajoa (Bondar, 1938) have been recorded on P. edulis, with the occurrence on the plants being the result of high infestation levels on preferred species nearby (Mendonça et al., 2011). Though the specific feeding preferences for these mites was not recorded (in the study cited here) they are known to feed on the upper surfaces of leaves of other plant species and at high densities on fruit (Mendonça et al., 2011).

Nematodes, especially the rootknot nematodes (Meloidogyne incognita, M. javanica and M. arenaria), are serious pests of P. edulis grown as a crop. Practical control measures are crop rotation and the use of tolerant rootstocks. The cocoa mirid Helopeltis clavifer, the passion vine bug Leptoglossus gonagra and the green vegetable bug Nezara viridula suck and pierce leaves and young fruits; these, together with the leaf-eating caterpillar Tiracola plagiata, are minor pests. Fruit flies that feed on passionfruit include the oriental fruit fly (Bactrocera dorsalis), the melon fly (B. cucurbitae), the Mediterranean fruit fly (Ceratitis capitata) and the Queensland fruit fly (B. tryoni). Pierced young fruit shrivels and falls; later injuries cause damage which lowers the grade. 

Mealybugs (Planococcus citri) occurring as a crop pest are usually controlled by their natural enemies (Cryptolaemus montrouzieri). The same applies to scales and mites which incidentally do much damage: the red scale (Aonidiella aurantii) and soft brown scale (Coccus hesperidum), as well as the red spider mite (Brevipalpus papayensis) and the passion vine mite (Brevipalpus phoenicis).

Diseases

The most important disease worldwide is brown spot (Alternaria passiflorae) on leaves, vines and fruits. Phytophthora blight (Phytophthora nicotianae) causes the wilting of shoot tips and crown rot, particularly where water stagnates occasionally. Septoria spot, caused by the fungus Septoria passiflorae, causes extensive spotting of leaf and fruit, and occasionally of the stem (Inch, 1978). Fusarium wilt is caused by the soilborne fungus Fusarium oxysporum f.sp. passiflorae; the shoots wilt, followed by a complete collapse of the plant.

A number of viruses have been reported where P. edulis is grown as a crop, notably passion-fruit woodiness potyvirus (PWV) and passiflora latent carlavirus (PLV). They are spread by aphids (Aphis gossypii, Myzus persicae) and pruning knives. Other virus diseases are ring-spot from Côte d'Ivoire, which is similar to PWV.

A much longer list of actual and potential pests and diseases has been compiled for a quarantine pest risk assessment for plants imported from Chile (Firko and Podleckis, 1996). It is difficult to determine which pests and diseases in that report are significant for plants growing in the field.

Environmental

• Agroforestry
• Amenity

General

• Botanical garden/zoo
• Ornamental

Human food and beverage

• Beverage base
• Fruits
• Oil/fat
• Spices and culinary herbs

Medicinal, pharmaceutical

• Traditional/folklore

Ornamental

• Propagation material
• Seed trade

A number of Passiflora species are generally similar; close similarities are discussed in Bernacci et al. (2008) and a useful key for distinguishing a large number of species in the genus is given in the Flora of China (Yinzheng et al., 2007). The key to the different taxonomic sections or series of Passiflora shows that P. edulis is from section Passiflora, making it broadly similar to the other members of the section e.g.; P. incarnata, P. cincinnata,P. filamentosa, P. recurva, and P. trintae (Cervi, 1997). However, the phylogenetic relationships place it within a large clade of 60 species (Muschner et al., 2012).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

P. edulis is regarded as a minor weed, or locally serious problem and a common garden escape with local impacts. In the Galapagos islands, 3% Roundup (glyphosate) and 3% Combo (picloram and triclopyr combined) have been used to control the plant (Renteria et al., 2006). More than 10,000 plants were removed on Raoul Island (one of the Kermadec Islands) using a mix of hand weeding and herbicidal treatment (West, 2002).

In high value preserves on Maui, Hawaii, a mix of hand weeding and herbicidal cut and stump painting using herbicides has been used on this species (Holt, 1992). It has not been considered for biocontrol (Froude, 2002) though a number of generalist pests are known from its native and introduced range (Inch, 1978; Firko and Podleckis, 1996). Grazing can prevent establishment and spread of this plant in some situations (Lusweti et al., 2012).

More work, using modern methods, needs to be done to determine the phylogenetic (including genetics and morphological) relationships between the recognized forms and between regional populations. It may be difficult to discern what its true native range is, but some effort to clearly describe it using objective criteria could be worthwhile.

27/06/14 Updated by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA

03/01/13 Original text by:

Christopher E Buddenhagen, Florida State University, USA