How to care for mexican petunias?

How to Care for a Mexican Petunia

A Mexican petunia, or Ruellia brittoniana, is easy to grow under most conditions. These plants will produce blooms in almost any type of soil, and are resistant to both drought and wet conditions as well. Mexican petunias are perennial shrubs, which can grow as tall as three feet, but in cold climates Mexican petunias can be grown as annuals that must be replanted every year. There are also some dwarf species available, which will grow only to less than one foot. With minimal care and supervision, these plants produce attractive, tubular flowers which are generally bluish or purple in color, and similar in appearance to common petunias—even though the two plants are not related. These plants are very attractive to butterflies, which makes them popular choices in many yards.

Tip: Gardeners seem to either love Ruellia, or dislike its invasive nature. In some areas of the country, a sterile version of Ruellia, which will not re-seed, can be found at nurseries and garden centers.

Soil and Planting Site

Mexican petunias, also known as desert petunias, produce more flowers the more sunlight they have, so choose a sunny spot in your yard. Though Mexican petunias are highly adaptable to most soil types, they grow better in fertile soil that is well drained and capable of retaining the required amounts of moisture. Amend the planting spot with some mature compost, and remove all weeds four to five weeks before planting. Soil drainage can be improved by incorporating some sand and thoroughly mixing it in with the soil. The roots are very easily formed in such a planting spot, in the right temperature and climate. The best time to plant Mexican petunias is early spring, when there is no chance of frost. Once established, the plant will bloom profusely throughout the warmer periods of the year.

You can easily propagate these plants with cuttings, seeds, or by divisions.


Once established, Mexican petunias are very hardy, and can survive for long spells without water. However, young plants need regular watering. You can also grow these plants indoors in pots, provided they have a sunny location. Indoor plants must be watered regularly as well during hot weather. Keep them away from any heat vents and electrical equipment.

In the winter, indoor Mexican petunias must only be watered when the soil shows signs of drying. These plants are highly resistant to most pests and diseases.


In warmer climates, Mexican petunias can grow rapidly and propagate themselves by way of seeds. In some areas, this plant is considered an invasive species because they can spread very fast, taking over the yard if not controlled. If you feel that these pretty plants are taking over your yard, you can easily pull out the required number of stems. These shrubs also need their woody and tough stems regularly pruned to maintain their shape and appearance.

If you want more of these beautiful flowers in your backyard, cutting stems halfway after flowering will result in the growth of several more stems and flowers. In colder climates, the foliage will be damaged by frost, in which case the damaged parts must be removed and disposed of promptly to avoid infection.

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Winter hardy to USDA Zone 8 (marginally hardy in Zone 7 with protection and mulch) where it is best grown in medium to wet soils in full sun to part shade. Best flowering is in full sun. This plant thrives in moist, fertile, humusy but well-drained soils. It is a versatile plant that tolerates an extremely wide range of growing conditions. It thrives as a marginal water plant and in boggy soils. It also does well in average garden soils with even moisture. Established plants have respectable drought tolerance. Plants also tolerate high heat and humidity. Cut back stems after flowering to encourage new flowers. Plants will spread by rhizomes and self-seeding in the garden, and have escaped gardens and aggressively naturalized in parts of the southeastern U. S. Notwithstanding its value as an excellent flowering plant, this species is currently listed as a Category One invasive species by the Florida Exotic Pest Plant Council (FEPPC) because it has been found to invade natural areas and displace native flora in the State of Florida. Plants are most invasive in moist areas. Invasiveness is clearly not a problem in St. Louis, however, where these plants are grown as annuals, with stem cuttings overwintered indoors if desired. Easy to propagate by cuttings, division and seed.

Ruellia simplex, commonly called Mexican petunia or Texas petunia, is a vigorous, shrubby, woody-based, rhizomatous perennial that is grown as an annual north of USDA Zone 8. It is native to Mexico, but has escaped gardens and naturalized somewhat aggressively in parts of the southeastern U. S. from South Carolina to Texas plus Hawaii, Puerto Rico and the U. S. Virgin Islands. It typically grows to 3-4’ tall in the wild, but to 2-3’ tall in gardens. Plants branch from the ground into several woody-based stems clothed with elongated, linear, willow-like, dark green leaves (to 6-12” long and ¾” wide) that are often tinged with purple. Tubular, trumpet-shaped, 5-lobed, petunia-like, lavender to violet flowers (to 1.75” long) bloom from the upper leaf axils in loose purple-stemmed clusters (long-stalked cymes). Each flower blooms for only one day. Best flowering occurs in the deep South near the temperatures of its Mexican origin where flowers may appear from May to November, but sometimes year round. Flowering is very respectable but less frequent when plants are grown as annuals in northern gardens where they typically bloom from May to September. Flowers are followed by bean-like pods (to 1” long) which explosively dehisce ripened seed in all directions.

Considerable confusion has existed over the years as to the correct specific epithet for this plant. It is been given a number of different names, including R. brittoniana, R. coerulea, R. malacosperma and R. tweediana. At this time, Ruellia simplex is the preferred specific epithet because it has been determined that this was the name first given to this plant in 1870 when it was described in Cuba, and accordingly that name has priority.

Ruellia simplex


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.” Scientific names include Ruellia brittoniana, R. coerulea and R. tweediana, 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. It was introduced to Florida in the 1940s. Since then it has naturalized in most counties in Florida, plus in six other southern states, Hawaii, Puerto Rico and the Virgin Islands.

Mexican-petunia can thrive in a range of environments, including flatwoods, hardwood hammocks, prairies, rivers and pastures. It can withstand both wet and drought conditions, full sun and shade. Mexican-petunia is highly invasive and since 2001 it has been listed as a Category 1 invasive species by the Florida Exotic Pest Plant Council, described as “plants that are altering native plant communities by displacing native species, changing community structures or ecological functions, or hybridizing with natives”. The UF/IFAS Assessment of the Status of Non-Native Plants in Florida’s Natural Areas finds Mexican-petunia to be invasive in all zones in Florida.

There are tall cultivars of Mexican-petunia (“Purple Showers,” pink-flowered “Chi Chi,” and white-flowered “Snow White”) as well as dwarf cultivars (“Katies”) in the three flower colors. All these cultivars, with the exception of “Purple Showers” are fertile and potentially invasive. In 2012 and 2013 three new sterile cultivars developed at UF were released: “Mayan Purple,” “Mayan White,” and “Mayan Pink.”

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Mexican-petunia 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.

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Mexican-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. Mexican-petunia can also resprout from crowns or rootstocks when cut back or killed back by frost.

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Control in invaded natural areas as well as control at the propagule source (home-gardens and landscapes) is needed for long-term management of this invasive species. Reinvasion and/or occurrence of new invaders can be a problem in home-gardens; therefore we recommend that herbicide treatments be followed by replanting with native or appropriate non-aggressive ornamental plants.


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.” Native alternatives to Mexican-petunia for use in home landscaping include wild petunia (Ruellia caroliniensis), blue curls (Trichostema dichotomum), butterflyweed (Asclepias tuberosa), or swamp milkweed (Asclepias perennis).


Wild Mexican-petunia must be removed completely, both above and belowground, or it will continue to resprout. Mowing, tillage or weed-eating the tops off Mexican-petunia will not remove the plants entirely. Instead, plants can be dug up with a shovel, with the aim to remove the entire root mass.


There are no known biological control agents for Mexican-petunia.


If the area of established wild Mexican-petunia is large, then an herbicide application might be needed. Many ready-mixed and readily available herbicides can successfully reduce Mexican-petunia cover, including glyphosate, which can be purchased by home-owners at most retail garden stores under the trade name Roundup. A single spray of a 2% foliar application of glyphosate will control small areas of Mexican-petunia; however, if the area of established plants is large or especially dense, then a second herbicide application may be needed after 2 to 3 months. Glyphosate can be applied at any time of year for Mexican-petunia control in the home-landscape. If you are planning to apply an herbicide, be aware of and follow all instructions and safety precautions outlined on the package.

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References and Useful Links

Freyre R. and S.B. Wilson. 2014. Ruellia simplex R10-105-Q54 (“Mayan Pink”). HortScience 49(4):499-502 .

Krumfolz, L.A. and S.B. Wilson. 2002. Varying growth and sexual reproduction across cultivars of Ruellia brittoniana. SNA Research Conference, Vol 47, p. 99.

Langeland, K.A. and K. Craddock Burks. 1998. Identification and Biology of Non-Native Plants in Florida’s Natural Areas. IFAS Publication SP 257. University of Florida, Gainesville. 165 pp.

Floridata Homepage

The Hillsborough County Invasive Species Task Force – Identification and control of non-native invasive plants in the Tampa Bay Area

Invasives and Exotic Species of North America

Pacific Island Ecosystems at Risk (PIER). Plant Threats to Pacific Ecosystems

Unites States Department of Agriculture Natural Resources Conservation Service Plants Database

University of Florida Center for Aquatic and Invasive Plants

University of Florida’s Cooperative Extension Electronic Data Information Source


Freyre, Rosanna
Research Scientist, UF/IFAS Environmental Horticulture Department, Gainesville

Adams, Carrie Reinhardt
Assistant Professor, UF/IFAS Environmental Horticulture Department, Gainesville

Wilson, Sandra B.
Professor, UF/IFAS Department of Environmental Horticulture
Indian River Research and Education Center


1. Identification and Biology of Nonnative Plants in Florida’s Natural Areas – Second Edition, by K.A. Langeland, H.M. Cherry, et al. University of Florida-IFAS Publication # SP 257. 2008.

3. Invasive and Non-native Plants You Should Know – Recognition Cards, by A. Richard and V. Ramey. University of Florida-IFAS Publication # SP 431. 2007.

Ruellia Simplex

Beloved by many gardeners for its heat tolerance and shade-loving nature, but reviled by others for its eagerness to spread with abandon, R. simplex can be divisive. Thanks to its sweet purple flowers, however, we come down firmly on the pro-ruellia side of the debate.

With forms tall and short, this evergreen, herbaceous perennial — hardy in USDA Hardiness Zones 8-11 — deserves consideration for inclusion in southern gardens. The tall version forms clumps 18 inches across, while the short type forms 12-inch clumps.

It’s an erect, often-multi-stemmed plant with dark green, droopy, slender, and long leaves. It’s especially loved for its papery, trumpet-shaped flowers that mimic every shade of the purple rainbow, as well as white and pink.

Sadly, each lovely flower lasts just a day. But fret not — the plant produces a succession of profuse two-inch flowers daily from spring through fall.

Let’s learn more about this lovely but divisive plant, and why Floridians want nothing to do with it! Here’s what we’ll tackle in this article:

If you live in Florida, you’re certainly excused from reading this article, though you might want to check below for a cultivar that is safe to grow in your region. Or perhaps you’d like to learn about growing turmeric, which also does quite well in the Sunshine State.

Ruellia simplex can be grown in either the shade or full sun, and is great for edging or mass plantings.

Interestingly, the stem of this plant becomes more purple when it’s in bright light, as opposed to when it’s grown in a shady area, where the stem stays fairly green. I’ve always used my Mexican petunia as a shade plant and was surprised to see purple-stemmed ruellia on a visit to Tucson, Arizona, where it was planted in full sun.

Cultivation and History

As with so many of our favorite botanicals, this one comes with a host of aliases. Though not closely related to petunias, many know the plant as Britton’s wild, Texas petunia, or sometimes even Mexican bluebell.

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.

The plant is native to Mexico and South America, and has naturalized in Hawaii and from South Carolina to Texas, where gardeners appreciate it greatly. Butterflies like it too — it attracts swallowtail, brush-footed, and monarch butterflies eager to enjoy the flowers’ nectar.

However, as alluded to above, it is considered invasive in Florida. There, like a septuagenarian Minnesotan in January, it has populated freely, and the locals RUE(llia) the day it was introduced. It has a tendency to crowd out native Florida species, and so local horticulturists strongly warn against its use.

The plant is named for Jean de la Ruelle, a late fifteenth- to early sixteenth-century French herbalist and physician to King Francois.


Mexican petunia spreads naturally by both seeds — it can spew the small brown discs as far as ten feet — and rhizomes.

Photo by Gretchen Heber.

You can also propagate this plant via purchased seeds, cuttings, or division.

From Seed

Sow R. simplex seeds in early spring, after all danger of frost has passed. Plant one to two seeds for each expected plant, spaced 12 inches apart.

From Cuttings

If you want even more plants — in a different part of the yard, for example — you can propagate by taking cuttings in springtime.

With a sharp, clean blade, cut a healthy-looking stem just below a node, 4-6 inches from the end. Strip off any leaves near the bottom of the stem, and remove the bloom.

Prepare a clean 4-inch pot with a mix of perlite and peat moss and moisten the mixture. Make a 2-inch-deep hole in the potting mix with a pencil.

Dip the cut end of the cutting into a powdered rooting hormone, and place the cutting into the hole you made in the potting mix.

Place your potted cuttings in bright, indirect light, and keep them moist. After roots are established, you can transplant them outside.


To divide this plant, loosen the soil around the area, and then dig around the clump you wish to excise.

Lift out the clump and, using a shovel, slice the crown of the plant into several pieces. Place your transplants into holes the same depth as the root balls of your clumps and twice as wide. Spread the roots out in the holes.

Cover the roots with dirt and water thoroughly; continue to water well for several weeks until well-established.

Get more details about dividing perennials here.

How to Grow

Mexican petunia is generally highly prized as a shade plant, but if your summers aren’t too brutal, the plant may be able to take full sun.

It is drought tolerant, and in fact, throughout our brutal Central Texas summers, I give mine nary a drop of supplemental water and they do just fine. However, the plant does even better in wet conditions (hello, Florida!).

As with most plants, you’ll want to treat them to regular, deep waterings immediately after transplanting, which you’ll do in springtime, and then you can back off the watering if you like.

You can baby the plant with rich compost or you can stick in the native soil that’s already there, and it will still do fine.

Fertilize with a 10-10-10 mixture in springtime. Or don’t. See a theme here?

Growing Tips

  • Don’t plant in full sun if the heat is brutal where you live
  • Give the plant extra water right after you plant it
  • Plant in sun or shade

Pruning and Maintenance

Trim out any dead leaves and remove dead flowers for aesthetic purposes. Cut off the seed pods if you don’t want the plant to spew its seeds. You can dry and save them for planting elsewhere if you wish, or trade with the neighbors.

Photo by Gretchen Heber.

Of course, if your R. simplex spreads too far and wide, you can excise the metastasizing plants.

Cultivars to Select

Several cultivars are available, with the distinguishing characteristic typically being flower color.

Ruellia Rooted Live Plants via Amazon

A notable and popular cultivar differs from the straight species in its height. While most standard forms of Mexican petunia range in height from 18 to 36 inches, ‘Katie’s Dwarf’ ranges from eight to 12 inches tall.

‘Purple Katie’ Mexican Petunia

This variety is less aggressive than its taller cousins, though mine definitely spreads. Packages of 50 seeds are available from Amazon.

Pink Mexican Ruellia Petunia ‘Chi Chi’

‘Chi Chi’ is a popular pink cultivar often found at plant centers, or you can purchase a packet of 35 seeds today on Amazon.

Floridians, if you’re still with us, you should choose the cultivar ‘Purple Showers,’ which is sterile and does not produce seed.

Ruellia Simplex ‘Purple Showers’

It can still spread via rhizomes, however.

Established plants in three-gallon pots are available via Amazon.

Managing Pests and Diseases

It’s not on the menu for deer, but if these graceful herbivores are helping themselves to other plants in your garden, check out this article about protecting your plants.
R. simplex doesn’t have any notable insect pest or disease concerns to worry about, either.

Best Uses

Mass plantings of the tall type make a nice border for the back of your beds, whereas the shorter variety makes a lovely edging plant.

You also might want to use ruellia to add some color to shady areas.

Mexican Pansy Quick Reference Chart

Plant Type: Perennial Flower Color Purple/violet
Native To: Mexico and South America Tolerates: Drought
Hardiness (USDA Zone): 8-11 (marginally hardy in Zone 7 with protection) Maintenance Minimal
Bloom Time: Spring, Summer, Fall Soil Type: Any
Exposure: Sun or shade Soil PH: Any
Time to Maturity 1-2 months Soil Drainage: Well-draining
Spacing 12 inches Companion Planting: Lantana
Planting Depth: 1/4 inch Uses: Tall type – borders and mass plantings
Dwarf type – edging
Height: 8-12 inches (dwarf type)
18-36 inches (tall type)
Family: Acanthaceae
Spread: 24-36 inches Subfamily: Acanthoideae
Water Needs: Consistent moisture Genus: Ruellia
Pests & Diseases: Spider mites Species R. simplex
Attracts: Butterflies (swallowtail, brush-footed, and milkweed) and hummingbirds

Floridians notwithstanding, gardeners in the southern United States would do well to add this purple-blooming beauty to their gardens. A lovely tall plant for the back of a bed, or a pretty edging for the front — one species, two practical uses.

Photo by Gretchen Heber.

Virtually maintenance-free and pest-free, and requiring hardly any attention, R. simplex is a lovely addition to any garden.

Are you in the pro- or anti-ruellia camp? Share your experience with this pretty plant in the comments section below.

If you found this guide valuable, you’ll also find some good info here:

  • How to Grow and Care for Salvia
  • Full-sun Flowering Perennials for Southern Gardens
  • Learn How to Grow Asparagus Fern
  • Grow Coneflower, A Native American Favorite


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Photos by Gretchen Heber © Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Product photos via liveplantflower, SVI, andlvrgarden. Uncredited photos: . With additional writing and editing by Allison Sidhu.

About Gretchen Heber

A former garden editor for a daily newspaper in Austin, Texas, Gretchen Heber goes through entirely too many pruners and garden gloves in a year’s time. She’s never met a succulent she didn’t like and gets really irritated every 3-4 years when Austin actually has a freeze cold enough to kill them. To Gretchen, nothing is more rewarding than a quick dash to the garden to pluck herbs to season the evening meal. And it’s definitely time for a happy dance when she’s able to beat the squirrels to the peaches, figs, or loquats.

What Is Ruellia Wild Petunia: Learn About The Care Of Ruellia Plants

Easy to care for and great for use as coverage, ruellia plants offer unique beauty to landscape areas. So, what is ruellia and can this Mexican native be cultivated in our own home garden landscape? Keep reading to learn more about growing ruellia.

What is Ruellia?

Ruellia flowers are 2-inch long funnel-shaped blooms growing on a perennial shrub. Originally native to Mexico, it is now found in the Southwest United States, naturalized in many areas. Ruellia flowers from mid spring through the first frosts of fall with purple or blue blooms (on occasion red or pink) on purple stems.

The widely adaptable Ruellia brittoniana, also known as Mexican petunia, Mexican barrio, Mexican bluebell and most commonly wild petunia, has an equally spreading habitat of about 3 feet with low drooping branches and linear serrated leaves of a variegated purple hue.

Care of Ruellia Plants

Not only is ruellia an evergreen, but it is a relatively hardy variety despite its penchant for warmer temperatures. Although the care of ruellia plants indicate thriving in very warm climates, these wild petunia plants can actually survive winters in the 20’s and 30’s. Ruellia flowers will generally die back at the foliage tips below 32 degrees F. and all the way to the ground in the 20’s. However, upon a return to more seasonable temperatures, the ruellia wild petunia will bounce back with as much vigor as before.

When thinking about the care of ruellia plants, you will want to keep in mind that the wild petunia aggressively self sows and care should be taken to contain the plants. Due to this self-sowing, the plant makes an ideal container or planter specimen serving to impede the rampant spread likely to occur when directly planted in the garden landscape.

Requirements for Growing Ruellia

An ideal location for growing ruellia is a site with full sun exposure. Although ruellia flowers are highly adaptable and may do well in shade, expect fewer blooms due to the lack of sunlight. Growing ruellia plants appreciate regular water but again the tolerant plant can withstand drought conditions in prepared soil.

This upright to spreading perennial can be propagated via seed, vegetative cuttings or root divisions and should be trimmed to tame the self-seeding, rampant growth. Also, remove any frost damaged foliage to prevent any further damage or insipient disease.

Care of ruellia plants is best in USDA hardiness zones 8b through 11. Ruellia flowers may be planted year round in all zones and used either in container gardening, as mass plantings or ground cover where they are terrific attractors for butterflies.

Some varietals of wild petunia include:

  • ‘Chi chi’ – variety with pink flowers
  • ‘Icicles’ – type that blooms all white
  • ‘Baby Katie’ – dwarf variety only about one foot tall with purple flowers

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