Mexican petunia is a lovely perennial with blue to purple flowers that can be found in select garden centers.
Due to its three-foot height, Mexican petunia has long been employed by gardeners to heighten perennial borders.
However, Florida has designated Mexican petunia (Ruellia simplex*) as a severely invasive plant. This implies that it can wriggle out of backyard gardens and spread into the wild, displacing native species.
Unless you can buy a variety like “Purple Showers” that has been studied and expressly found not to be invasive, you shouldn’t put Mexican petunia in your yard.
Ruellia caroliniensis, a native wild petunia, is also present but is less common. You can protect Florida’s natural regions for future generations to enjoy by making wise decisions and refraining from planting invasive plants.
(*Note: Due to taxonomy regulations, the Latin name of the Mexican petunia has changed numerous times. Enough said. If you buy a Mexican petunia plant, make sure it’s either the caroliniensis variety, which is endemic to the area, or a sterile cultivar. If in doubt, check with the vendor.)
How can you prevent the proliferation of Mexican petunias?
A yard or garden bed can be swiftly overrun by Mexican petunias. Several measures can be taken to prevent Mexican petunias from encroaching in other places.
To slow down and restrict the spread of the plant, bury wood planks approximately six inches thick around it.
A larger Mexican petunia should be planted in a pot and placed in an established garden. Before the plant needs to be repotted, the roots will expand within the pot and let it to blossom wonderfully for years.
The plant will be forced to develop as a ground cover without encroaching on other parts of the garden if it is placed in a walled area far from other plants.
Mexican petunia seeds can disperse, so if you find a sprout in a spot where you don’t want the plant to grow, pull it out as soon as you can to prevent it from setting roots and creating a problem.
From Cuttings
You can increase the number of plants in your yard, for instance, by taking cuttings in the spring.
Cut a healthy-looking stem four to six inches from the end, just below a node, with a clean, sharp blade. Remove the bloom and any leaves that are close to the stem’s base.
Perlite and peat moss should be prepared in a clean four-inch pot and moistened. With a pencil, dig a two-inch-deep hole in the potting soil.
Place the cutting into the hole you produced in the potting soil after dipping the cut end of it in a powdered rooting hormone.
Keep your potted cuttings moist and in bright, indirect light. You can transplant them outside once the roots have taken.
Division
To divide this plant, aerate the surrounding soil and then excavate the desired clump.
Lift the clump out, then use a shovel to cut the plant’s crown into many pieces.
Put your transplants into holes that are twice as broad and the same depth as the root balls of your clumps. In the holes, distribute the roots widely.
When the roots are well-established, keep watering them well for many weeks after covering them with earth and watering them well.
Do dwarf Mexican petunias spread quickly?
We cultivate plants for a variety of reasons, including the food they generate, the fragrant blossoms, the vibrant foliage, and more.
The plant I’m thinking of is one of those that is known to be invasive and is still offered for sale in garden centers despite spending more than 15 years on the Florida Exotic Pest Plant Council’s Category I list. Mexican petunia, once known as Ruellia brittoniana and currently known as Ruellia simplex, is the plant I want to warn you about.
Let me first clarify the distinction between aggressive and invasive plants.
Although native plants, such as elderberries, can become aggressive in disturbed regions, they don’t disrupt the ecology and support local insects and fauna since they are native.
Birds disperse plants that provide berries, such as the exotic Brazilian pepper tree, which can eventually cover great distances. Exotic or non-native plants have the potential to establish monocultures in natural regions, displacing native species.
I only recently discovered the damage invasive plants do to our yards and natural spaces. I viewed Doug Tallamy’s webinar entitled A Guide to Restoring the Little Things that Run the World, which was held by the Florida Wildflower Foundation.
Insect populations are already at dangerously low levels, and they are at the base of the terrestrial food web. Supporting our local and migratory birds, as well as our native bees, is essential, and the prevalence of invasive exotic species in yards and wild areas is exacerbating this issue.
Ruellia simplex, the Mexican petunia, is a hardy plant that grows gorgeous purple flowers, but beware—it may quickly spread throughout your entire yard and beyond. The Florida Exotic Pest Plant Council classified Mexican petunia as a Category I invasive exotic in 2001 after it was introduced to Florida in the 1940s.
Because they supplant native plants, affect the ecosystem, modify ecological processes, and hybridize (cross pollination) with native species, Category I plants are the most harmful. Mexican petunia has been deemed an invasive species in north, central, and south Florida by the UF/IFAS Assessment of the Status of Non-Native Plants in Florida’s Natural Areas.
It’s crucial to get rid of Mexican petunia as soon as you can if you have them in your yard. Even once they are gone, you will still have work to do since you must watch out for the emergence of new plants.
Be prepared to do that for more than a year as you continue to eliminate them as soon as you find them.
There is good news if you adore Mexican petunias. The sterile “Purple Showers” cultivar can be planted despite not producing any viable seeds. The UF also created the sterile cultivars “Mayan Purple,” “Mayan White,” and “Mayan Pink.”
The cultivars “Chi Chi,” which has pink flowers, “Snow White, which has white flowers, and the dwarf cultivars of the “Katies series,” which have purple, pink, and white flowers, are all considered invasive and yield viable seed.
Grow Carolina wild petunia, Ruellia caroliniensis, the sole native species of this genus, if you want to grow dwarf plants.
Lantana and porterweed are two examples of non-native plants that have crossed-pollinated (hybridized) with native species.
Florida now has lantana camara growing naturally everywhere, including at the bottoms of fence posts and in wide-open spaces.
Lantana canescens, sometimes known as hammock lantana, is a bushy plant that bears extremely tiny heads of white flowers with a yellow center. Along the edges of the hammocks in Miami-Dade County, this species can be found.
Native wild sage, L. involucrate, is an erect, bushy shrub that blooms with white flowers that frequently have a violet hue and yellow centers. The central and southern counties are home to this species.
L. depressa, our final native plant, is endemic to Florida, is listed as threatened, bears yellow blooms, and has three distinct variants that differ depending on where it is located.
Lantana depressa var. floridana is the indigenous variety that can be found in Brevard County.
Because it produces vibrant pink and yellow or orange and yellow blooms in the same inflorescence, the invasive lantana L. camara is simple to spot.
There have been reported deaths here in Florida from this lantana species, which is also extremely deadly to both people and livestock. When eaten, the unripe, green fruits are lethal.
In addition to naturalizing all over the state, Lantana camara also contaminated the gene pool of the three native species of Lantana depressa. The Lantana camara cultivars “Gold Mound,” “New Gold,” “Alba,” and “Partiot” are deemed infertile by the EPPC.
“Bloomify Red” and “Bloomify Rose” are likewise recognized as “not a problem species” by the UF/IFAS Assessment of Non-native Plants.
Another illustration of a non-native plant interbreeding with a native plant in Florida is porterweed, which I previously described.
Stachytarpheta jamaicensis, a low-growing groundcover that matures to a height of 1 foot, is our native blue porterweed. Additionally, the state is home to Stachytarpheta urticifolia, a non-native woody shrub that can reach heights of 4-6 feet.
The seedlings produced by the cross-pollination of these two species are known as S. x intercedens, and they have a maturity height of 2-3 feet, which suggests that they are mathematically inclined.
Weeding is probably the least enjoyable aspect of gardening, so why add a plant that could take over your yard, community, and possibly the entire state?
The Mexican petunia should be avoided the next time you visit a garden center. It has spread throughout Florida, as well as to six other southern states, Hawaii, Puerto Rico, and the Virgin Islands. You should also inform your family, friends, and neighbors about its undesirable traits.
How quickly does the Mexican petunia grow?
Mexican petunia, also known as desert petunia, quickly takes root when you start with a seedling or young plant that has been produced in a nursery. Typically, clusters of 3 foot tall, sturdy, semi-woody stalks bearing lovely leaves and blooming within a month or two are produced. The plant’s first season typically features purple flowers that bloom from mid-spring until late-fall. Placing the plant in full light will encourage quick, healthy growth and an abundance of blossoms. This will also encourage the development of flower buds and keep the leaves a deep, rich green.
Do Mexican petunias appeal to hummingbirds?
Our friend gave us some unidentified seeds about three years ago. They came from a “dark green plant with blue blossoms that resembled crepe paper. They were positioned by our garage in a garden nook. We quickly developed a dark green shrub with serrated leaves that eventually produced beautiful blue tubular blooms. It refroze during the winter and then reemerged in the spring. AND it spread, but we discovered that the tiny self-seeded plants were simple to remove.
Without success, I tried to identify this plant. I thoroughly read the Sunset Western Garden Book, consulted other gardeners who visited our garden, and, in the end, gave up the search. Then, last week, when on a trip with the Vaca Valley Garden Club at High Hand Nursery in Loomis, I came across our plant. It is a Mexican petunia, or Ruellia brittoncana. The mysterious plant was finally identified and given a name.
Research revealed that this plant is native to Mexico and is simple to grow in either dry or moist soil. They are evergreen shrubs that reach heights of 3 feet and a width of 4 feet. There are a few dwarf kinds available, like “Katie,” which reaches a height of 10 inches. These plants produce flowers in a variety of blue, purple, or white hues with little care. The two plants are not related, despite the fact that they resemble the petunia bloom we are all familiar with. Because the plants’ vibrant blossoms draw butterflies and hummingbirds, many home gardeners grow them.
Due to its invasiveness, Ruellia is either adored or despised by gardeners. There is a sterile variety with deep purple flowers named “Purple Showers” that will not self-seed. Even though it won’t reseed, if cultivated in wet soil, it can spread by its roots. They are also known as desert petunias and grow more flowers the more sun they get. Mexican petunias can be propagated through division, seeds, or cuttings.
Once established, plants planted in the early spring will bloom all through the summer and into the fall. Although young plants require routine watering, the plant is sturdy enough to endure prolonged periods of dryness. They adapt quickly and thrive in containers as long as they get sunlight. The best news is that Ruellia brittoncana is very resilient to the majority of illnesses and pests.
Do you need to reduce your Mexican petunias?
Typically, a Mexican petunia only needs one annual pruning in late winter or early spring to remove any damaged, weak, or unwelcome stems back to the plant’s root system. During the flowering season, trimming spent flower stalks helps keep the garden looking tidy. Every few years, in the spring, trim Mexican petunia clumps back to a few inches above the ground to revitalize them.
The spread of this plant can be controlled with specific pruning methods. Cut off any spent Mexican petunia blooms before they set seed and pluck away any stems that have fallen to the ground and become rooted in the soil.
Can I grow Mexican petunia?
Mexican petunia, often known as ruellia, may add color and height to your summer borders. This low-maintenance plant grows to a height of 3 feet (although there are dwarf types that stay shorter) and produces waves of petunia-like blue, white, or pink flowers throughout the summer. The colorful insects swarm to the fragrant petals of Mexican petunia, making it a perfect choice for butterfly gardens. Additionally, Mexican petunia is a necessary plant for butterfly gardens because various species of butterflies need it as a host plant for their larvae to feed on. Mexican petunia will frequently self-sow after it is established and spread widely in the garden, so plant it in areas where you can monitor it or in sizable container gardens. Deer can’t eat Mexican petunia. Hardy in zones 9 through 11.
Questions about Mexican Petunias Send us an email, and one of our flower planting specialists will respond.
Mexican Petunia Growing Instructions
It thrives and blooms best in broad sun or light shade for Mexican petunia. Although it can grow in the shade, it won’t blossom as much and will appear lanky and leggy. Mulch the plants to maintain regular soil conditions, especially in hot, dry weather, as this sun-loving perennial prefers rich, somewhat damp soil. Mexican petunias can be grown as annual flowers in the northern hemisphere. Mexican petunia may spread quickly, so plant it in an area where you can limit it.
Restrictions may apply to some of these plant’s varieties since they are thought to be invasive. Before planting, check the local laws. At Costa Farms, only non-invasive hybrids are grown.
h5#These types go well with Mexican petunias: