Passion

Usually, when passion is mentioned, we think of sexual passion. But in the fifteenth century, people were more likely to be referring to religious passion. And that is what the missionaries who arrived in South America saw when they looked at the parts of this flower. Wikipedia explains it clearly: 

Symbols of the last days of Jesus and especially his crucifixion:

Blue passion flower (P. caerulea) showing most elements of the Christian symbolism

• The pointed tips of the leaves were taken to represent the Holy Lance.
• The tendrils represent the whips used in the flagellation of Christ.
• The ten petals and sepals represent the ten faithful apostles (excluding St. Peter the denier and Judas Iscariot the betrayer).
• The flower's radial filaments, which can number more than a hundred and vary from flower to flower, represent the crown of thorns.
• The chalice-shaped ovary with its receptacle represents a hammer or the Holy Grail
• The 3 stigmas represent the 3 nails and the 5 anthers below them the 5 wounds (four by the nails and one by the lance).
• The blue and white colors of many species' flowers represent Heaven and Purity.

This plant isn't sacred in a strict sense, but the religious history is interesting. 

This plant is common in the Berkeley area. Generally people grow it because it is easy and has beautiful flowers. It also attracts butterflies. As I have mentioned before, Gulf Fritillaries lay their eggs on it. My plant (the photo at the top) is "Sally's Rescue," officially known as "Berkeley." The Wikipedia photo is P. caerulea, one of the most common. Both are favored by butterflies. They also have a fabulous tunnel of nectar hidden below the filaments, which bees love. 

Highly recommended for a chain link fence. But it grow ferociously. Be ready with the pruners.