Passion flowers grow on passion vines that can grow 15 to 20 feet in just one year and typically bloom in the spring. After pollination, the ovaries inside the flowers grow into fruit, the insides of which are edible. While you can harvest--or pick--passion flowers, it is more common to harvest them after they have turned to fruit and have ripened.
Wait until the flowers reach about 2 to 3 inches in diameter and have three large green leaves. In the center of the leaves are five greenish-white sepals with five white petals on top. The flowers are mature at this point and can be picked with a small pair of clippers; however, most people wait until the flowers turn to fruit to harvest.
Allow the flowers to die away and the ovaries inside the flowers transform into fruits, which are green at first. The fruits will continue to grow until they are about 1 1/2 to 2 inches wide.
Notice when the fruits change colors, which signifies a ripe fruit. This typically occurs 70 to 80 days after blooming. Passion fruit colors range from light yellow, orange and purple, depending on your passion fruit variety.
Harvest passion fruits each day as they begin to change colors. Either clip them off the vine or wait until they drop to the ground. The rinds are tough enough to withstand the fall and not hurt the edible seeds and juice inside.
Wash and dry your passion fruits and then store them in a plastic bag. Keep for two to three weeks at 50 degrees Fahrenheit. When the fruit begins to shrivel a bit, the seeds and juice inside are the sweetest.