QHI

I recommend Queensland Horticultural Institute for information and advice re growing Passiflora as a commercial crop. I am often asked if the common passion flower P. caerulea has edible fruit. They are edible when ripe (going from green to orange yellow) but are insipid and not recommended.

  Varieties

The most widely grown fruit are the hard shelled P. edulis varieties. These all germinate very readily and keep relatively well. Perhaps 40 or more Passiflora have fruit we would judge as edible, of those 10 or so may be grown as food crops for local consumption, but most of these have soft fruit which do not keep or travel well. e.g. P. tripartita var. mollissima and other Tacsonia which taste good but deteriorate quickly after harvest. See a variety of edible fruit images.

  Climacteric fruit
 
"Fruits and vegetables can be classified as climacteric or non-climacteric. Climacteric fruit continue to ripen after harvest, whereas non-climacteric do not. Ripening is a process that includes development of color, flavor and texture (softening).'' Elizabeth Baldwin USDA© Cirad 2001. Passion fruit are climacteric, other examples are banana, mango, papaya, avocado, and guava. This means that the ripening process continues after abscission (when the fruit drops). Compare this with the non-climacteric strawberry, an unripe strawberry never ripens once picked too early.

  Ripening

I think we tend to assume that once the passion fruit has dropped it is ripe. For some species e.g. Decaloba it may be, and for eating it may be, but to maximise chances of successful germination it will do no harm to leave the fruit in a sunny window for 1-2 weeks after it has dropped. Wild collectors report that fruit picked from the vine may contain viable seed though its keeping properties are reduced. This P. bogotensis fully ripe fruit, opened up the day it dropped, indeed shows seed at different stages of ripening. An adaptation perhaps so that even if an animal eats the fruit early instead of waiting for it to drop some seed will still germinate. In Guam P. suberosa fruit is eaten by bats that land on the forest canopy to eat them.

  Toxicity

I would recommend only eating ripe fruit from commercial sources like shops and markets. For more detail re toxicity, especially of the potentially dangerous unripe fruit even in edible species, see Passiflora toxicology. Generally the smell of cyanide and the taste will put anyone off eating the unripe fruit. In the interests of science I have carefully tasted small amounts of ripe fruit of many Passiflora species. Please do not try this yourselves. See the hybrid and species pictures section where the taste of most that have fruited will be recorded. Many like P. caerulea and any hybrids with caerulea as a parent are bland, some taste dreadful (P. kermesina) and some taste toxic (P. trisecta), perhaps safe for certain animals only. There is also a question over the safety of P. manicata fruit. It is known in Ecuador as 'diablito' because of its hallucinogenic properties.