It's a Passiflora sp. which of itself is not unusual, it was growing outside which again of itself is not unusual but then I saw this and my interest was roused.....
In English it's usually known as Banana Passionfruit. In South America this would be known as curuba, tacso or tumbo. Botanically it has almost as many names. The plant was identified as P. mollissima but that is not a good name. It's actually either P. tripartita var. mollissima or P. tarminiana. There was some splitting and I won't know which side of the split this is until (if) it flowers.
According to Lost Crops of the Incas (my go to guide for south american edibles) it...
seems to have been domesticated shortly before the Spanish Conquest. Today, it is cultivated in home gardens and commercial orchards, and the highly prized fruits are regularly available in local markets. Colombia has some outstanding varieties; it has begun exporting the fruits, and has established a national committee to study the biology and agronomy of this species. 6Naturally I had to have one to go with my other Incan edibles and helpfully they had some strong young plants available....
Curuba juice is considered the finest of all passionfruit juices, and a wine is made from it. The fruits are also used in jams, jellies, and gelatin desserts. In addition, the pulp is strained (to remove the seeds), blended with milk and sugar, and served as a drink called “sorbete de curuba.” It is also made into ice cream. Combined with alcoholic liquors (aguardiente) and sugar, it is served as a cocktail.
This is so going up my wall. Incidentally:
a) there are other banana passionfruit sp. including P. mixta which I grew for years with never a sign of a flower.
b) this plant is apparently doing well naturalising up chainlink fences in areas of LA with an ecuadorean community.
c) less happily it's a problematic invasive in Hawaii, PNG and NZ so think carefully if you're Passiflora-ing up in the tropics.
d) the skin is weirdly soft which confused my camera's autofocus terribly.
e) yes that post title is a beach boys pun.