|Petunia exserta flower|
Petunia is genus of 20 species  of flowering plants of South American origin. The popular flower of the same name derived its epithet from the French, which took the word petun, meaning "tobacco," from a Tupi–Guarani language. An annual, most of the varieties seen in gardens are hybrids ( P. × atkinsiana, also known as P. × hybrida).
The Mayan and Incas believed that petunias have the power to chase away (with their odor) the underworld monsters and spirits. Their flower-beds were bunched together for magical drinks. According to the folklore, Petunias will thrive where there is positive energy and will not grow in places where there is negativity. 
When given as a gift, Petunias typically have two meanings. They could represent being comfortable with someone, or "your company suits me".  Conversely, they could also represent anger and resentment. 
Petunia is a genus in the family Solanaceae, subfamily Petunioideae. Well known members of Solanaceae in other subfamilies include tobacco (Nicotianoideae), and the cape gooseberry, tomato, potato, deadly nightshades and chili pepper (Solanoideae).  Some botanists place the plants of the genus Calibrachoa in the genus Petunia,  but this is not accepted by others.    Petchoa is a hybrid genus derived from crossing Calibrachoa and Petunia. 
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.  
The tubular flowers are favoured by some Lepidoptera species, including the Hummingbird hawk moth.  The flowers are eaten by the larvae of the corn earworm, Helicoverpa zea and the cabbage looper, Trichoplusia ni. 
Petunias can tolerate relatively harsh conditions and hot climates. They need at least five hours of sunlight every day. They grow well in low humidity, moist soil. They can be grown from seeds. Watering once a week should be sufficient in most regions. Hanging baskets and other containers need more frequent watering.  Maximum growth occurs in late spring. Applying fertilizer monthly or weekly, depending on the variety, will help the plant grow quickly. Petunias can be cultivated in hanging baskets.
In horticulture many terms are used to denote different types of cultivated petunias. These include Grandiflora, Multiflora, Wave (Spreading), Supertunia, Cascadia, and Surfinia.
Many species other than P. × atkinsiana are also gaining popularity in the home garden.  A wide range of flower colours, sizes, and plant architectures are available in both P. × atkinsiana and other species, listed below: 
Species include: 
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- Ellis, Barbara W. Taylor's Guide to Annuals. Boston. Houghton Mifflin Co. 1999. Print.
- The Plant List: Petunia
- Ando, T, Kokubun, H., Marchesi, E., Suárez, E. & Basualdo, I. 2005. Phylogenetic Analysis of Petunia sensu Jussieu (Solanaceae) using Chloroplast DNA RFLP. Ann. Bot. 96(2): 289 - 297. 
- Mishiba, Kei-Ichiro; Ando, Toshio; Mii, Masahiro; Watanabe, Hitoshi; Kokubun, Hisashi; Hashimoto, Goro; Marchesi, Eduardo (2000). "Nuclear DNA Content as an Index Character Discriminating Taxa in the Genus Petunia sensu Jussieu (Solanaceae)". Ann Bot. 85: 665–673.
- The Value of Growing Petchoa SuperCal®. Ornamental News Oct 25 2012
- Ando, T., Nomura, M. Tsukahara, J., Watanabe, H., Kokubun, H., Tsukamoto, T., Hashimoto, G., Marchesi, E., Kitching, I.(2001) Reproductive isolation in a native population of Petunia sensu Jussieu (Solanaceae) Ann. Bot. (Lond.) 88:403–413.
- Griesbach, R.J.(2007) in Flower breeding and genetics: Issues, challenges and opportunities for the 21st century, Petunia, ed Anderson N.O. (Springer, Dordrecht, The Netherlands), pp 301–336.
- Butterfly Conservation
- Johnson, ET; Berhow, MA; Dowd, PF. "Colored and white sectors from star-patterned petunia flowers display differential resistance to corn earworm and cabbage looper larvae". J Chem Ecol. 34: 757–65. doi: 10.1007/s10886-008-9444-0. PMID 18484139.
- Brown, Deborah. “Growing Petunias” University of Minnesota Extension Office. University of Minnesota. 2009. Web. 25 June 2009. http://www.extension.umn.edu/distribution/horticulture/DG1120.html
- Allan M. Armitage, Armitage's Manual of Annuals, Biennials, and Half-Hardy Perennials (Portland: Timber Press, 2001).
- The Plant List, retrieved 13 September 2015
|Wikispecies has information related to Petunia|
|Wikimedia Commons has media related to Petunia.|
- The Petunia Platform - a platform for Petunia-related research