Ruellia L. | The Wild Petunias

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GARDENING | PLANT ID

ACANTHUS FAMILY

 Ruellia               __________________

Ruellia is exogenous of flowering plants commonly known as ruellias or wild petunias. They are not closely related to petunias.

Initially, I planted a purple SOFTSEEDED WILD PETUNIA or BRITTON'S WILD PETUNIA (formerly a hybrid Mexican petunia), 
Ruellia simplex C. Wright in a 1 meter x 1 meter bed and over several years the ruellia has become exclusively pink. My ruellia, pictured, are not invasive nor aggressive. It is in a partially shaded area. I mistakenly thought this was a wild petunia native to Texas. It is sold in the nursery trade as a bedding plant that performs well and can be found as a dwarf called Katie's dwarf ruellia. Avid horticulturists across the land often get frustrated when attractive, floriferous, versatile, durable, and easy-to-grow plants get sidelined because they have been declared an invasive species. Ruellia simplex (commonly known as Mexican petunia) was declared a category 1 invasive in 2001 by the Florida Exotic Pest Plant Council, described as “a plant that is altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives” (Source: UF/IFAS Center for Aquatic and Invasive Plants).

There are 5 native species of Ruellia in Texas. These 5 species are:

1. DRUMMOND'S WILD PETUNIA - Ruellia drummondiana (Nees) A. Gray
2. FRINGELEAF WILD PETUNIA, WILD PETUNIA, LOW -  RUELLIA,  Ruellia humilis Nutt.
3. METZ'S WILD PETUNIA - Ruellia metzae Tharp.
4. WILD PETUNIA, VIOLET WILD PETUNIA - Ruellia nudiflora (Engelm. & A. Gray) Urb.
5. WESTERN WILD PETUNIA - Ruellia occidentalis (A. Gray) Tharp & F.A. Barkley.

See the chart at the bottom for all accepted ruellia species in the world as determined by the International Botanical Congress.

Ruellia simplex C. Wright – softseed wild petunia, Britton's wild petunia

 Ruellia simplex C. Wright – softseed wild petunia, Britton's wild petunia
 Sometimes you don't know what you will find until you take a closer look.

The genus was named in honor of Jean Ruelle, herbalist and physician to Francis I of France and translator of several works of Dioscorides.

Ruellia L. Seed pod

Species Characteristics

The former MEXICAN (WILD) PETUNIA has been reclassified as SOFTSEED WILD PETUNIA OR BRITTON'S WILD PETUNIA, Ruellia simplex C. Wright – It is a perennial in zones 8 to 11 that stands up to 3 feet in height. Stems are green or purple and leaves are dark green, oppositely arranged and lance-shaped, roughly 6 to 12 inches long and ½ to ¾ inches wide. Veins are prominent on the underside of the leaf. Leaf margins are can be smooth or wavy. Flowers are trumpet shaped (1-1/2 to 3 inches in diameter), solitary or borne in clusters at the tips of the stems, and are attractive to butterflies, bees and other pollinators. In fertile forms, cylindrical fruit or capsules containing 4 to 28 seeds are produced. Capsules have explosive dehiscence and seeds are spread long distances. Seeds produce a gel-like substance when wet that enables them to stick to surfaces when they dry. Seeds generally have high germination rates, and can germinate in both light and dark conditions. Stands of Mexican-petunia can also spread via underground stems or rhizomes. Ruellia simplex is a perennial growing 3 ft (0.91 m) tall, forming colonies of stalks with lance-shaped leaves that are 6 to 12 in (15 to 30 cm) and .5 to .75 in (1.3 to 1.9 cm) wide. Trumpet shaped flowers are purple and pink, with five petals, and 3 in (7.6 cm) wide. 

SOFTSEED WILD PETUNIA is able to tolerate a wide range of environmental conditions including variations in light, temperature, and moisture. Other characteristics that make wild Mexican-petunia a successful invasive are its rapid growth rate, affinity for disturbed locations, prolific production of seed, and lack of germination requirements such as scarification or stratification. Established plants can further spread by rhizome production. SOFTSEED WILD PETUNIA  can also resprout from crowns or rootstocks when cut back or killed back by frost. If you're purchasing a "wild petunia" plant, be sure it's either a native species or a sterile cultivar.  

It is important to install appropriate plant material into bare areas in the home-landscape. Bare ground can quickly become invaded by weeds or different invasive species common to urban areas. Installing appropriate non-invasive or native ornamental species into newly bare ground right away provides sufficient plant competition to hold the space. Use sterile Ruellia cultivars such as "Mayan Purple," "Purple Showers," "Mayan Pink" and "Mayan White."  There is a dwarf variety, "Katie" that is only 1 ft (0.30 m) tall.

The native Mexican species, Ruellia simplex with the common name Mexican Petunia or Briton's petunia. Mexican-petunia (also known as Mexican bluebell or Britton's petunia) is described as a "hardy perennial edging plant for flower beds and as colorful groundcovers." Scientifically, it’s been labeled R. brittoniana, R. coerulea, R. malacosperma, and R. tweediana, though today’s taxonomists are in agreement that R. simplex is the correct moniker. Scientific names include Ruellia brittoniana, R. coerulea, R. tweediana,  or Ruellia malacosperma (USDA NRCS 2016; Wundelin et al. 2016) but taxonomists now use the name Ruellia simplex, which was the first name used to describe this species. The wild form has purple flowers, and is native to Mexico, Western South America and the Antilles. Use the nomenclature Ruellia simplex for identification, as voted on by the Botanical Congress.

It was introduced to Texas and Florida in the early twentieth century and since then it has naturalized in many southern states.  R. Simplex is on the Texas Invasives list and the University of Florida's Center for Aquatic and Invasive Plants list.  Its seed dispersal mechanism is one reason that it is able to invade new areas so easily.

References                                                                                           

• Tharp, Benjamin C, and Fred A. Barkley. Genus Ruellia in Texas. Notre Dame, Ind.: University of Notre Dame, 1949. Print.
• Sandra B. Wilson, Adrienne Burkhead, Carrie Reinhardt Adams, and Rosanna Freyre, Natural area weeds: Mexican Petunia (Ruellia simplex).
• Freyre et al. 2012, Fruitless Ruellia simplex R10-102 ('Mayan Purple') and R10-108 ('Mayan White').
• Freyre et al. 2012, Breeding and evaluating for landscape performance and fruitlessness in Mexican petunia (Ruellia, Acanthaceae).
• Freyre et al. 2012,  Ruellia simplex R10-105-Q54 ('Mayan Pink').
• Hammer 2002; Gilman 1999; Wirth et al. 2004; Bechtloff et al. 2019.  
• Wunderlin, Richard P, and Bruce F. Hansen. Guide to the Vascular Plants of Florida. Gainesville, FL: University Press of Florida, 2011. Print
• Ezcurra, C.; Daniel TF, 2007. Ruellia simplex, an older and overlooked name for Ruellia tweediana and Ruellia coerulea.
• Khoshoo, T N, R C. Mehra, and K Bose. "Hybridity, Polyploidy and Change in Breeding System in a <i>ruellia</i> Hybrid." Theoretical and Applied Genetics : International Journal of Plant Breeding Research. 39.3 (1969): 133-140. Print.
• International Journal of Plant SciencesVolume 174, Number 1
• The Tripp Report, Tripp, Erin.        https://trippreport.com/Disentangling geographical, biotic, and abiotic drivers of plant diversity in neotropical Ruellia (Acanthaceae). Ruellia Floral Color.      https://trippreport.com/ruellia-floral-color/

• Daniel, T. F. and T. I. Chuang. 1998. Chromosome number of cultivated Acanthaceae and systematic implications. Pp. 309-330 In: Mathew P., Sivadasan M. (eds.) Diversity and taxonomy of tropical flowering plants. Mentor Books. Calicut, India.

• Wasshausen, D. C. 2005. Chapter 5.6 Acanthus: Family Acanthaceae. Pp. 112-114. In: G. A. Krupnick and W. J. Kress (eds.). Plant conservation: A natural history approach. University of Chicago Press, Chicago.

• Tripp, E. A., T. F. Daniel, S. Fatimah, and L. A. McDade. 2013. Phylogenetic relationships within Ruellieae (Acanthaceae) and a revised classification. International Journal of Plant Science 174: 97-137.

• Tripp, E. A. 2007. Evolutionary relationships within the species-rich genus Ruellia (Acanthaceae). Systematic Botany 32: 628-649.

• Grant, W. F. 1955. A cytogenetic study of Acanthaceae of Thailand. Brittonia. 8: 121-149.

• Daniel, T. F. 2004. Acanthaceae of Sonora: Taxonomy and Phytogeography. Proceedings of the California Academy of Sciences 55: 690-805.

• Ruel, Jean. De Natura Stirpium Ll. Iii. Basil: Hier. Frobenius et Nic. Episcopius, 1543. Print.
• ITIS, Integrated Taxonomic Information System, accepted and not accepted nomenclature for ruellia, Link

TABLE I:  ACCEPTED RUELLIA SPECIES (ITIS.GOV)

Ruellia blechum L. – Ruellia blechum L. – Browne's blechum

Ruellia brevifolia (Pohl) C. Ezcurra – tropical wild petunia

Ruellia caroliniensis (J.F. Gmel.) Steud. – Carolina wild petunia

Ruellia chartacea (T. Anderson) Wassh. – Peruvian wild petunia

Ruellia ciliatiflora Hook. – hairyflower wild petunia

Ruellia ciliosa Pursh – Sandhills wild petunia

Ruellia coccinea (L.) Vahl – yerba maravilla

Ruellia corzoi Tharp & F.A. Barkley – Corzo's wild petunia

Ruellia davisiorum Tharp & F.A. Barkley – Rio Grande wild petunia

Ruellia devosiana hort. Jacob-Makoy ex E. Morren – Brazilian wild petunia

Ruellia dipteracanthus Hemsl.

Ruellia drummondiana (Nees) A. Gray – Drummond's wild petunia

Ruellia drushelii Tharp & F.A. Barkley – Drushel's wild petunia

Ruellia fulgida Andrews

Ruellia heteromorpha Fernald – Carolina wild petunia

Ruellia humilis Nutt. – fringeleaf wild petunia, wild petunia, low ruellia

Ruellia metzae Tharp – Metz's wild petunia

Ruellia noctiflora (Nees) A. Gray – nightflowering wild petunia

Ruellia nudiflora (Engelm. & A. Gray) Urb. – wild petunia, violet wild petunia

Ruellia occidentalis (A. Gray) Tharp & F.A. Barkley – western wild petunia

Ruellia parryi A. Gray – Parry's wild petunia

Ruellia patula Jacq.

Ruellia pedunculata Torr. ex A. Gray – stalked wild petunia

Ruellia pinetorum Fernald – stalked wild petunia

Ruellia prostrata Poir. – prostrate wild petunia

Ruellia purshiana Fernald – Pursh's wild petunia

Ruellia simplex C. Wright – softseed wild petunia, Britton's wild petunia

Ruellia strepens L. – limestone wild petunia

Ruellia succulenta Small – Carolina wild petunia

Ruellia tuberosa L. – minnieroot

Ruellia yucatana (Leonard) Tharp & F.A. Barkley – violet ruellia, Yucatan wild petunia blechum

Old Botanical Illustrations

  Ruellia haenkeanus (Nees.) Wassh., (found currently as Stemonacanthus) Curtiss, W. Botanical Magazine (1800 - 1938), International Journal of Plant SciencesVolume 174, Number 1

Ruellia strepens L. – LIMESTONE WILD PETUNIA 
Frederick A. Stokes Company 1899
Artist: Alice Lounsberry*
North American

Ruellia strepens L. – LIMESTONE WILD PETUNIA 
Artist: Dill, H.
North American

Ruellia Ciliosa LONG TUBED RUELLIA

Artist, Thomas Meehan 1878

Classification update 2021

Ruellia ciliosa Pursh – SANDHILLS WILD PETUNIA

References                                                             

ITIS  Integrated Taxonomy Information System

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