From World Seed Supply: “Petunia violacea, also known as Shanin, is an annual garden flower that blooms through the summer months. The plant produces ornamental funnel-shaped flowers that also bear some resemblance to tobacco flowers. The flowers are a bright magenta with dark throats much like the flowers of mirabilis multiflora. This species, also known as wild petunia, is endemic to South America. Albert Hoffman and Richard Shultes reported that the Indian tribes of Ecuador and Argentina used the petunia violacea to induce a reaction in the body similar to the sensation of flight. Modern study on the phenomenon is limited, and chemicals have not been isolated that could account for these effects. With other similar species native to the same regions, it is always possible that the identities of the plants used by these people have been confused. But the Solanaceae family is well-known for plants that have been associated with witchcraft and shamanism, namely belladonna, datura, hyoscyamus niger, and of course tobacco. Petunia is now grown in gardens all over the world and has been hybridized to create the numerous varieties that you tend to see in garden centers. But if you’re looking for the original genetics, this is the variety is what you want.
Plants will do best in soil enriched with organic matter. It does not like the cold weather and likes full sunlight. But at the same time, it does not like extremely hot temperatures. The soil should be very well drained and loose. Depending on the soil type and the size of the pot, you may be able to get away with letting the rain water your plants. Otherwise, you’ll want to water before the soil dries out completely.
Planting should occur once temperatures are at least 65-70° F. To prevent damage during the cold months, it is recommended to cover the soil with dry leaves or straw as a measure of insulation. During the summer when the temperatures reach 90° and above, they can begin to look straggly and have fewer blooms. In this case, they can be cut back a couple of inches, fertilized with compost tea and watered more often.”