I have previously tried to grow a Passiflora arida (Baja passion flower) from seed, but I was unsuccessful. Aside from wanting the plant itself, I wanted to attract Gulf Fritillary butterflies. They use various species of Passiflora as a host plant, meaning that they lay their eggs on the plant and the caterpillars eat it. Most butterflies will go to any flower for nectar but they will use plants from only a selected family, genus or species as their host. In the absence of a P. arida I decided to just go to the nearest nursery and buy a passion flower. Below is the plant I bought and a good view of the flower. Most passion flowers are vines. I planted this one in a container and started training it up a post.
I don't know what species/variety it is and I don't care. I just wanted something to attract the butterflies. It worked immediately. In the photo above you can see that some of the leaves have already been chewed. The Gulf Fritillary butterflies found it right away and started laying eggs on it. Below is the butterfly in the process of egg laying.
Sometimes there would be several butterflies on the vine at the same time. Soon the eggs hatched and the caterpillars became large enough to be readily visible.
The vine grew rapidly, but the egg laying and caterpillar chewing of the leaves was even more rapid. Soon the caterpillars had entirely stripped the vine of leaves. That's okay with me because I want the butterflies, not the plant. The plant is still alive, though leafless, and dozens of butterflies still come around every day. The plant must put out a chemical signal that attracts them, even the bare stem.
Now the caterpillars have been replaced by cocoons. They are everywhere in the vicinity of the plant. They resemble a dried leaf, which is excellent camouflage. Also, passion flowers contain a chemical which is ingested by the caterpillars and makes the adult butterflies somewhat toxic to birds and other predators. This mechanism is very similar to the relationship between Monarchs and Milkweeds.