P. apetala
Minimum temperature: 5°C [41°F]
Flower diameter: 1cm [0,5"]
Minimum temperature: 5°C [41°F]
Flower diameter: 1cm [0,5"]
P. apetala has (as is the botanical name already says) no petals.
There is next to the smallest P. allantophylla passion flower, but has much larger leaves than P. allantophylla.