The summer of the year 2008 was been the most fantastic for rainforest vines. Plants growing and flowering which we have never seen before and Passiflora herbertiana is one of those. It was so exciting when its blunt little leaves emerged last year, and we have waited patiently for it to grow and reveal itself to be a native passionfruit.
Australia is home to only three endemic species of passionfruit, compared to tropical South America which has 400 species, and one of ours is Passiflora herbertiana.
It is a rainforest climbing plant which uses curly tendrils growing at the base of leaf stalks to hold itself in place and to make its way up and through rainforest trees into the sunlight.
The leaves are quite unusual in shape when the plant is young: an elongated oval with a middle bump to one side. The stems, leaf stalks and the under surface of the leaves are finely hairy though you will need a hand lens to see them clearly.
As the plant matures the leaves change shape and become up to 12cm wide, with 3 broad, almost acute lobes. If you see a newly emerging seedling of a Passiflora herbertiana you could be forgiven for believing it to be a different plant altogether.
One distinguishing characteristic of Passiflora herbertiana is the presence of two raised glands at the top of the leaf stalk. The purpose of this gland is not clear, though ants have been seen apparently feeding there.
Passiaflora herbertiana prefers the sunlight available at the rainforest edge or in partly cleared areas in preference the shade in the centre of a rainforest.
The plant occurs from north eastern NSW to north eastern Queensland in Australia. It is quite hardy and will grow happily in many different soils, from sand to heavy clay, but it thrives best in very wet springs/summers, so it enjoys lots of moisture. The plant is often not seen during droughts at all, only to reappear when the rain comes. It is not clear whether the root remains underground waiting for the right conditions or whether it re-grows from seeds lying dormant in the soil.
The flower buds begin green and then become an orange shade.
The flowers occur singly in the leaf axils but as all the axils have a bud, the flowering season is quite long, mainly from August to December. The plant can spot flower at other times if conditions suit. The flowers are about 6 cm across and are interesting in shape and colour.
The flowers emerge from the orange bud a creamy yellow and a day or so later become pale orange before they shrivel away.
The fruit is green with white spots, and about 1/2 the size of the black passionfruit, which is generally Passiflora edulis, that we commonly see for sale in the supermarket. Passiflora herbertiana is tinier but tasty. The fruit matures over a period of a few months. They can look very warty.
That could be because something is piercing the skin to suck out the fluids, or something is growing inside and emerging through a hole from the fruit at maturity. A weevil which looks like the Elephant Weevil (Orthorhinus cylindrirostris) has appeared on the fruit, and there is a larva inside some of the fruit. Most references to this weevil seem to be referring to the stems of grapevines, and the damage their larvae cause there. However as both the weevil and the passionfruit are native to Australia it seems appropriate that they exist together in this way.
So far only one of the fruits has reached maturity without being attacked, and it was delicious.