|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 ( Petunia × atkinsiana, also known as Petunia × hybrida).
Petunia is a genus in the family Solanaceae, subfamily Petunioideae. Well known members of Solanaceae in other subfamilies include tobacco (subfamily Nicotianoideae), and the cape gooseberry, tomato, potato, deadly nightshade and chili pepper (subfamily 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. 
Species include: 
- Petunia alpicola
- Petunia axillaris
- Petunia bajeensis
- Petunia bonjardinensis
- Petunia exserta
- Petunia guarapuavensis
- Petunia inflata
- Petunia integrifolia
- Petunia interior
- Petunia ledifolia
- Petunia littoralis
- Petunia mantiqueirensis
- Petunia occidentalis
- Petunia patagonica
- Petunia reitzii
- Petunia riograndensis
- Petunia saxicola
- Petunia scheideana
- Petunia villadiana
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, but not frost. They need at least five hours of sunlight every day and flourish in moist soil and conditions of low atmospheric humidity. They are best grown from seed. 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 Petunia × atkinsiana are also gaining popularity in the home garden.  A wide range of flower colours, sizes, and plant architectures are available in both Petunia × atkinsiana and other species, listed below: 
The Maya and Inca believed that the scent of petunias had the power to ward off underworld monsters and spirits. Their flower-buds were bunched together for magical drinks. According to New Age folklore, Petunias will only thrive where there is "positive energy" and will not grow in places where there is "negativity". 
When given as a gift, Petunias have ( in the language of flowers ) two mutually exclusive meanings, symbolising on the one hand being comfortable with someone,  and on the other anger and resentment. 
Petunia, Violet, In NIT Agartala, India
A form of Petunia axillaris
White Petunia axillaris
Leaves of Petunia × atkinsiana
- "The plant list: Petunia". Royal Botanic Garden Kew and Missouri Botanic Garden. Retrieved 17 March 2018.
- “Classification for Kingdom Plantae Down to Family Solanaceae”. Natural Resources Conservation Service. United States Department of Agriculture. 2009. Web. July 8, 2009. 
- 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
- The Plant List, retrieved 13 September 2015
- 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).
- "Complete Guide: How to Plant Petunias". J. Parker's. Retrieved 22 May 2018.
- "Petunia Flower: Its Meanings and Symbolism". Flower Meaning. Retrieved 22 May 2018.
- "Petunia Flower – Meaning, Symbolism and Colors". Flower Meanings. Retrieved 22 May 2018.
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