Passionvine Family Planning

Passiflora incarnata
Passiflora incarnata

I post pics of my volunteer Passionvine every year. (Passiflora incarnata.) I’ve talked about the extravagant exoticism of this native flower,
the Christian symbolism devised by early missionaries,
the fact that it is Tennessee’s official state wildflower,
that it is the host plant for Gulf Fritillary butterflies,
and that the wrinkly yellow fruit is delish.
But I’ve just learned something new: the flowers are smart. The vine knows how much fruit it can tolerate bringing to bear, and it adjusts the flowers accordingly. All passionvine flowers have male and female parts, but not all the flowers are arranged to achieve fruitful pollination.

The first pic shows a functional bisexual flower: the three female bits (the topmost forms visible) lean down, the better to receive pollen from the male anthers (which hang upside down so the bees will brush up against them whilst collecting nectar).

The second pic shows the female bits sticking almost straight up, away from the pollen. It isn’t likely that even this big carpenter bee will accidentally brush against those erect stigmas and transfer pollen to them.

Of course, I am greedy and want all the fruit this vine will give, so I’ve already hand-pollinated the “functionally-male” flower to see what will happen. The ovary is not visibly swelling yet, but time will tell.

Carpenter bees are one of passionvine's prime pollinators
Carpenter bees are passionvine’s prime pollinators. Look at that pollen on its back! They are the ideally sized “connectors” between the nectar carpet below, and the hanging anthers above (where the pollen waits). As they forage for sweets, their fuzzy backs rub against the pollen. And, as they visit flower to flower, the wearable pollen grains mix and mingle, and eventually make contact with a stigma.