Passion Fruit

What is passion fruit?

Passion fruit is not one plant but a group of fruits from the genus Passiflora. They are evergreen climbers that pull themselves up with coiled tendrils and carry the elaborate flowers whose corona of threads gave the genus its name. Inside every fruit sit many seeds, each wrapped in a juicy, aromatic aril.

At Sa Medada five species grow next to one another. They share the climbing habit and the seed-filled fruit, but they come from very different climates.

Origin and growth

Purple passion fruit (Passiflora edulis). The purple form is native from southern Brazil through Paraguay to northern Argentina. It is the most widely grown and, for gardens outside the tropics, one of the hardiest of the edible species. The fruit is round, about the size of an egg, and drops when ripe. The vines are vigorous but short-lived; the California Rare Fruit Growers give five to seven years.

Banana passionfruit (Passiflora tripartita var. mollissima and Passiflora tarminiana). Both come from the Andes and bear long, yellow, banana-shaped fruit with soft skin and pink flowers. In Colombia the banana passionfruit is grown between 1,800 and 3,200 metres at mean temperatures of 13 to 16 °C. Passiflora tarminiana was only described in 2001; much older literature, including the Hawaiian, filed it under mollissima.

Giant granadilla (Passiflora quadrangularis). It has the largest fruit of the genus, 10 to 30 cm long according to Morton, with thick, mild flesh around the seed cavity. It is a truly tropical plant that wants warmth day and night and the most frost-sensitive of the five.

Sweet granadilla (Passiflora ligularis). An Andean highland species, cultivated in Colombia between 1,800 and 2,600 metres at 15 to 23 °C. Its smooth, hard shell turns orange-yellow; inside lies grey-white, very sweet pulp.

Requirements

Cold. The purple passion fruit survives brief frosts to about -2 °C, and its roots often resprout after damage. UC Cooperative Extension gives a similar limit of about -2 °C for the banana passionfruit. The giant granadilla is by far the most sensitive.

Water. Regular moisture keeps the vines flowering. Demand peaks as the fruit ripens; drought makes fruit shrivel and drop early. Morton gives at least 90 cm of rain a year for the purple form.

Soil. Deep, very well drained, rich in organic matter, roughly pH 6.5 to 7.5. The roots are shallow, so a thick mulch helps.

Light and wind. Full sun for flowering, shelter from wind for the tendrils and leaves. The Andean species prefer cool nights.

Fruit, use and harvest

The purple passion fruit ripens 70 to 80 days after pollination and is gathered from the ground. It is self-fertile; carpenter bees pollinate it best. The giant granadilla often needs hand pollination within a few hours of the flower opening, and its unripe fruit is cooked as a vegetable in the tropics. The purple passion fruit and the giant granadilla are known to contain cyanogenic glycosides in leaves and young fruit; only ripe fruit is eaten raw.

Constituents and effects

The medicinal passionflower of European pharmacies is a different species, Passiflora incarnata from North America. For its dried herb the European Medicines Agency recognises a traditional use to relieve mild symptoms of mental stress and to aid sleep; the assessment rests on long, safe use, because the clinical evidence was judged insufficient.

For the fruit species grown here the evidence is thinner. Two small, double-blind, placebo-controlled trials from the same research group gave adults an extract of purple passion fruit peel, 150 mg a day. In 42 people with asthma, wheeze, cough and shortness of breath decreased over four weeks (Watson et al. 2008). In 33 people with knee osteoarthritis, pain and stiffness scores improved over two months (Farid et al. 2010). Both studies concern an extract, not the fresh fruit, both are small, and one of the authors is named as an inventor on patents for the extract. They are a lead for further research, not a proven effect.

In the food forest

Passion fruit occupies the climber layer of a food forest. It needs something to climb: a trellis, a fence, or a robust, light-crowned tree. In a plant guild it uses vertical space that other plants leave empty and fruits within a year or two, long before the trees do. In syntropic agriculture it is a plant of the early phases. Because the vines are short-lived, their pruned growth returns to the soil as mulch, and new plants follow from seed.

In the Mediterranean climate

Passion fruit is a common garden and market fruit on Madeira, and on São Miguel in the Azores the local passion fruit carries a protected designation of origin. In Sicily passion fruit is among the subtropical crops grown alongside mango and avocado. On a plantation near Orosei, about two hours north of Sa Medada, it has been bearing fruit for years. The difficulties are winter cold for the tropical species and summer drought for all of them; the Andean species also come from cool highlands, and how they cope with lowland heat is less settled than for the purple form.

The genus also teaches caution. Passiflora tarminiana became one of the worst invaders of Hawaiian forests; Passiflora tripartita var. mollissima is banned from trade in New Zealand; Passiflora edulis has naturalised in the Galápagos and is treated as an environmental weed in parts of eastern Australia. Birds and mammals spread the seeds. None of these species is on the EU list. In practice this means gathering fallen fruit and watching for seedlings in the surrounding scrub.

Propagation and care

Fresh seed germinates in 10 to 20 days. Cuttings of mature wood with three or four nodes also root. On soils with root diseases, grafting onto resistant rootstock is used.

How Terra Humana understands it

Passion fruit is meant to show at Sa Medada how quickly the vertical layer of a food forest can bear fruit, and how closely related plants from the lowlands and the high Andes behave on the same slope. Their known capacity to spread elsewhere is something we keep in view and answer with care, not something we look away from.