How to Grow Mexican Petunias (Ruellia simplex)

Mexican petunias

by Jennifer Poindexter

My favorite flower is the wave petunia, but did you know that petunias come in many varieties? One option is the Mexican petunia (Ruellia simplex), and I’m going to fill you in on what you should know about this plant.

Some gardeners love this flower. Others, not so much. However, I think it’s fair to learn what you can about these flowers, including how to grow them, to make that judgment call for yourself.

The reason some gardeners don’t love this flower is because it reseeds extremely easily and is even considered invasive in some areas.

Yet, other gardeners love this flower because it’s low-maintenance, hardy, and produces gorgeous blooms in shaded locations.

Here’s the information you need to decide if Mexican petunias have a place around your home:

Growing Conditions for Mexican Petunias

Do you live in an area with higher temperatures and plenty of shade? The Mexican petunia could be a great flower choice for you.

This plant tends to enjoy warmth but should be grown in partial shade. It can’t handle brutally cold temperatures or extremely bright sunlight.

However, don’t get the wrong idea. This is not a picky plant. It can grow in poor quality soil, but if you want to give it every reason to succeed, take the extra step to provide nutrient rich soil that’s well-draining and slightly loamy.

This flower is hardy in planting zones eight through eleven and should remain an evergreen perennial in such areas.

As if having a fuss-free flower isn’t enough, this plant also comes in a variety of options. You can pick short or tall varieties of Mexican petunia based upon your growing space.

The taller varieties grow to be approximately three feet in height. The shorter varieties grow to be a foot or less.

Mexican petunias are multi-stemmed plants that produce many blooms. They have the typical horn-shaped bloom, as most petunias do, and come in colors ranging from purple, pink, and white.

The blooms come in clusters and only last a day. However, don’t grow discouraged by this because the plant produces many blooms each day from spring through fall.

The benefit of growing Mexican petunias is they invite pollinators to your garden or yard. These flowers also grow well as a border plant, in a container garden, in rock gardens, or smaller garden plots.

Be aware, as previously mentioned, this flower is also considered invasive in some areas. Therefore, do your research about your particular area before adding this plant to your landscape.

As you can tell, Mexican petunias don’t require a lot from you. Yet, they still put on quite the show of color and beauty. If you need a perennial flower that isn’t picky about growing conditions, this could be the plant for you.

How to Plant Mexican Petunias

You can plant Mexican petunias using a variety of methods. The first way to plant this flower is from seed.

If you already have one of these flowers in your garden, you won’t need to plant anymore seeds. This flower will cast the seeds on its own for more to appear in the coming years.

However, if you’re adding this flower as a new addition or want to grow it in a different location, sowing seeds is very easy. You can amend the soil in the growing area if you desire. This isn’t required for the flower to do well as Mexican petunias are pretty sturdy.

Wait until all threat of frost is over in the spring. From there, till the earth and plant one to two seeds per foot in your growing location. The seeds should be planted about ¼ inch deep in the soil.

Be sure to keep the soil consistently moist until the seeds have sprouted.

The next option for growing Mexican petunias is to propagate them from a cutting of another plant. You should remove a piece of a mature plant using clean cutters.

The cutting should be approximately six inches long and taken right beneath a node. If the cutting has any leaves at the bottom, remove them. If there’s a bloom on the cutting, remove it as well.

Dip the cut end of the cutting in rooting hormone. Then place it in a container with soil that drains adequately.

The cutting should be planted two inches deep. Place the container in bright, indirect sunlight and keep the soil consistently damp while the plant is forming a root system.

Once the root system is fully established, you can transplant the flowers into their permanent growing location.

Our final method for propagating Mexican petunias is from division. This is done by dividing a mature plant.

Dig up a large, healthy plant. Ensure you remove the entire root system. Using a garden spade, divide the entire plant down the center. You should even divide the roots.

Transplant the newly divided plants into permanent growing locations in holes that are the same depth as the roots but two times the width.

Also, be sure you select a growing location that meets the few specifications that Mexican petunias need. 

Whether you’re trying to grow more Mexican petunias from your current plants or adding a new plant to your growing set-up, these methods should help you achieve your gardening goals.

Caring for Mexican Petunias

When caring for Mexican petunias, you’ll be glad to hear that they’re very low-maintenance. Everything on this list are things you can do but aren’t required.

Mexican petunias really only need to be watered when they’re first planted to help them become established.

Otherwise, they’re quite drought-tolerant and shouldn’t need anymore water from you unless you’re going through a time of severe drought.

However, some gardeners like to ensure their plants are very well cared for and wish to add more water to these flowers.

You can because Mexican petunias not only thrive in dry conditions but also in excessively damp conditions, too.

Therefore, if you’d like to water these flowers be sure to water them deeply. This means that you water the plants for longer periods of time, fewer days of the week.

By doing this, the roots get a drink at the time of watering and the ground around the flowers becomes saturated.

However, as the days pass, the roots will dig deeper in search of more water. This encourages stronger root systems and healthier plants.

Don’t add more water without testing the soil. Dip your finger into the dirt next to the flower. If the soil isn’t dry to your second knuckle, don’t add anymore water. Repeat the process as needed.

The next thing you can do for Mexican petunias is fertilize them once in the spring. Again, it isn’t necessary but if you’d like to know the plant has all the nutrients it desires, this is a great way to go about it.

Use an all-purpose fertilizer and follow the instructions provided on the product.

This next tip is something you’ll probably want to do. You should add mulch around your Mexican petunias. 

The reason being is it helps the plant retain water, but it also keeps weeds down. This is healthier for the plant and less work for you.

Finally, consider deadheading the plants and removing their seed pods. Deadheading these flowers will keep the plants feeling younger, healthier, and make them appear more vibrant.

Removing the seed pods is a great way to control reseeding to keep your Mexican petunias in check and only growing where you want them to.

If you’re searching for a flower that’s easy to care for, the Mexican petunia could be exactly what you need.

Garden Pests and Diseases Which Impact Mexican Petunias

The last thing we must discuss when growing Mexican petunias is how to protect them. Most flowers face numerous challenges in their growing space.

However, Mexican petunias aren’t one of them. The only disease which could be a concern to this plant is blight.

This usually occurs when the plants are growing in areas where the soil isn’t well-draining, or they’re planted too densely.

You can avoid this by planting in well-draining soil and by thinning your plants when necessary. Blight can also be treated using a fungicide. Be sure to remove any damaged parts of the plants as well. 

The only pests which tend to bother this flower are spider mites. You will typically see the home of the spider mites before you see the actual pest.

Dislodge the homes from your plants by spraying them, forcefully, with a water hose. From there, treat your flowers with an insecticide.

Stay alert to potential problems when growing Mexican petunias. The sooner you catch an issue, the easier it is to correct.

Mexican petunias are gorgeous flowers that can bring beauty to your home or garden space year-round.

Ensure this plant isn’t considered invasive in your area prior to planting. If it’s not, put these tips into practice and see what you think of this highly debated flower.

More About Mexican Petunias

Mexican Petunias with text overlay how to grow mexican petunias

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