Petunia is a trumpet shaped, widely-cultivated genus of flowering plants of South American origin, in the family Solanaceae. The popular flower got its name from French, which took the word petun 'tobacco' from a Tupi-Guarani language. Most of the varieties seen in gardens are hybrids (Petunia x hybrida).
The origin of P. x hybrida is thought to be by hybridization between P. axillaris (the large white or night-scented petunia) and P. integrifolia (the violet-flowered petunia). P. axillaris bears night-fragrant, buff-white blossoms with long, thin tubes and somewhat flattened openings. The species was first sent from South America to Paris in 1823. P. integrifolia has a somewhat weedy habit, spreading stems with upright tips, and small lavender to purple flowers. It was discovered in South America by the explorer James Tweedie, after whom the genus Tweedia is named, who sent specimens to the Glasgow Botanical Garden in 1831. Many open-pollinated species are also gaining popularity in the home garden. A wide range of flower colors, sizes, and plant architectures are available in both the hybrid and open-pollinated species.
Some botanists place the plants of the genus Calibrachoa in the genus Petunia. Botanically speaking, tobacco, tomato, potato, and petunia are all in the family Solanaceae.
Petunias are generally insect pollinated with the exception of P. exserta, which is a rare, red-flowered, hummingbird pollinated species. Most petunias are diploid with 14 chromosomes and are interfertile with other petunia species.