Mexican petunia (Purple showers, Texas petunia, tall Mexican petunia, purple ruellia, hardy petunia, Mexican bluebell, Britton’s wild petunia) is a 12 to 15 inches (30.5 – 38 cm) tall multifunctional plant. It is an ideal choice for growing in small spaces, rock gardens, containers, and borders. Also, many gardeners use this deer-resistant and salt-tolerant flower in erosion control.
Since beautiful pink or purple blooms of this plant attract bees, butterflies, and birds, you can use it as a valuable part of your butterfly garden. Mexican petunia originated in South America and Mexico, but nowadays it is widespread plant in Hawaii and Texas. However, if you live in Florida, avoid planting this species because it is considered invasive in this state.
Facts about Mexican Petunia
Mexican petunia was named after French herbalist Jean de la Ruelle. That fast-growing perennial with green leaves on purple or green stems looks like a wild bloom.
One German botanist gave the name to this flower in 1879 and made a real confusion. Therefore, we can find a few Latin names of the same plant.
It grows best in the marshy ground, around lakes, and in woodlands. The shortly-lived flowers of your 1 to 4 feet (30.5 cm – 1.2 m) tall bush will begin opening in early spring. You can expect continuous blooming until the first frost.
Nowadays, it is a forbidden plant in some states since it is considered quite invasive. The reason is its uncontrolled growth, which overtakes other plants in the garden. To make the situation worse, it forms long horizontal roots growing above and below the surface of the ground. Therefore, it is almost impossible to eradicate this plant.
Plus, after mature seed capsules burst open, they scatter seeds everywhere. It can remain in the ground for years and germinate when you least expect it.
Non-invasive Varieties Suitable for Your Garden
If you don’t want to get stuck with the garden full of highly invasive flowers, you should pick out non-invasive varieties.
If you prefer dwarf varieties, you can buy a lovely, small, less aggressive perennial shrub in a nursery or online. I like growing 6 to 10 inches (15 – 25 cm) tall dwarf variations like ‘Katie.’ It is an excellent lush ground cover thanks to its magnificent blooms appearing from June to autumn.
When the time for flourishing comes, you will enjoy vibrant, trumpet-shaped flowers, which are unusual bluish-purple color. Plus, the beautiful flowers are surrounded by lovely narrow, glossy-green, 1 to 3 feet (30.5 – 91.5 cm) long leaves.
The best news is that this variety of Mexican petunia sets very few seeds, and it won’t spread them aggressively.
Alba (Ruellia malacosperma) is a scarce variety of Mexican Petunia. I adore its impressive white flowers blooming on 36 inches (0.9 m) tall plant from May to September. You should try to purchase this flower online because it is lovely, easy-to-grow, and quite hardy.
There is also lovely ‘Purple Showers’ with large deep-purple flowers. It is sterile, and you don’t need to deal with any seeds at all. However, avoid growing this variety in the highly moist ground since it can spread by rhizomes.
Nowadays, there are a couple of entirely sterile cultivars such as ‘Mayan White’ and ‘Mayan Purple.’ If you plant them, you can enjoy their beauty without any fear of overcrowding your garden.
How to Plant Mexican Petunia in Your Garden
Propagation by seeds
Mexican petunia is basically a self-seeding flower, which is considered aggressive and invasive in a few states in the US. You don’t need to bother to sow seeds if you have at least one plant in the garden. It will do the entire job by itself.
To keep the plant under control, you should harvest seed capsules from plants in your garden after they turn brown in autumn. Let the seeds dry out and store them in a cold place until spring comes. However, it is quite likely that your seeds will sprout even if you sow them immediately after drying.
If you haven’t sowed this flower until now, you can purchase seeds in a nursery and start a new plant that way. Start planting them inside in a pot a few months before the beginning of the growing season in the region you live in.
If you prefer sowing seeds directly in the garden, you can do that in early spring. In that case, you should wait for first blooming a bit longer. It is always better to plant two seeds per an expected plant. Provide at least 12 inches (30.5 cm) of space between the future plants. Water abundantly and wait to see new seedlings.
Propagating by cuttings
If you are not patient and want to see your Mexican petunia blooming as soon as possible, you can propagate it through cuttings as well. Find healthy stems in spring, and cut them below the node, at least 4 to 6 inches (10 – 15 cm) from the end. Remove flowers and leaves at the stems’ bottom.
You need a 4 inches (10 cm) deep pot filled with the potting mix. Dip the cut ends into a rooting hormone and put them into the 2 inches (5 cm) deep hole, which you have made in the mix. Take care to space them at least 2 inches (5 cm) apart.
Water cuttings regularly and keep the pot in bright, indirect light until establishing the roots. Then you should transplant new plants in the garden. Most gardeners recommend autumn as the best period for transplanting this plant. Once established, they will thrive and start flourishing as soon as the temperatures increase in spring.
Propagating by rhizomes
Mexican petunia usually spreads by rhizomes. You can produce new flowers by cutting the connection between the mother plant and the new shoots.
After transplanting these pieces into the garden, young plants will grow quickly. The best of all is that you can expect them blooming very soon.
Propagating by division
Start the process of dividing by loosening the soil around the mother plant. Dig the ground around clumps carefully and pick them up with a shovel.
Cut clumps into a few pieces with a part of roots and plant them into separate holes. Take care that they are the same depth as the root balls and wide enough.
Fill the hole with the garden soil and water abundantly. Keep watering for several weeks until the new plant establishes well.
How to Care Mexican Petunia
This plant can grow in different types of soil, but it will thrive when the ground is fertile and well-drained. Surprisingly, even though this flower is drought-tolerant, it spreads quickly next to the rivers and lakes where the soil is marshy.
Also, although it prefers neutral to slightly acidic ground, your Mexican petunia will tolerate alkaline environments as well. In general, when this plant establishes roots properly, it will grow almost everywhere.
Mexican petunia prefers growing in shadow, but it can tolerate sunlight if you live in a region where summers are not too hot. In fact, this plant will bloom more abundantly if you provide at least six hours of indirect sunlight for it a day.
Moreover, the color of the stems will vary depending on the amount of light your plant gets daily. If the stem of your flower is purple, it means that you have chosen the right position with enough sun. Plants growing in shadow usually have green stems.
Mexican petunia is an ideal plant to grow in the dry environment, but you can plant it in the wetland area as well. Unfortunately, it is a flower intolerant to low temperatures and the frost.
Therefore, you can grow it as an annual in the region with hot summers but cold winters. If you want to save your plant for the following season, you should move it inside and keep it away from coldness.
Since Mexican petunia is a drought-tolerant plant, you won’t have problems with watering even in summer. On the other hand, it will thrive in the regions with a high level of humidity, including possible floods.
However, it will become lush and healthy only if you water it deeply and regularly after transplanting in spring. Once established, this plant is not very demanding. It will be enough to water it once a month from spring to autumn to keep the ground moist. Don’t water your plant throughout winter.
Add organic compost after planting to enrich the soil. Also, it is recommended adding 10-10-10 fertilizer in spring to provide necessary nutrients and encourage blooming.
If it is the first time for you to grow Mexican petunia, you should loosen the soil with a garden tiller before planting. Add mature manure or compost, and mix it with the ground. If you need to improve drainage, it is an excellent idea to add sand as well.
Try to avoid adding too much nitrogen in the soil to prevent lush growth of the leaves instead of abundant blooming. Solve the problem with an excessive amount of that mineral by adding mulch, which draws nitrogen away from the ground.
Add a 2 inches (5 cm) thick layer of mulch around your plant to prevent weed growth and to keep the ground moist.
Mexican petunia doesn’t need individual supporting. Plant it against a wall, and let it thrive without additional demands.
Pruning and deadheading
Regular pruning will help your plant stay healthy and beautiful. Cut dead leaves and flowers with garden cutting shears to allow abundant flourishing. Plus, you will prevent self-seeding by cutting off the seed pods.
If you grow your Mexican petunia as a hedge, pruning will be highly beneficial for it. Also, deadheading after the blooming period will encourage the growth of new flowers.
Always keep in mind that Mexican petunia is quite invasive. Therefore, pull out excessive stems to keep your plant under control.
Mexican Petunia Pests and Diseases
Mexican petunia is a resistant plant without severe issues with pests and diseases. If there are some problems they would be:
Cold weather will damage the whole plant, especially its leaves. They will become wilted and brownish. Prevent this problem by protecting your flower from the low temperatures. The best way is to keep it safe indoors until the weather becomes warmer.
It is not very likely that these pests will attack your plant, but it is possible. Solve the problem by spraying leaves with soap solution or an adequate insecticide. Cut infected parts of the plant and throw them into the trash.
A few years ago, some gardeners reported the occurrence of these fungi among Mexican petunias. This disease caused root rot as well as changes in the foliage. Leaves turned yellow, wilted, and died eventually.
To avoid such a problem, you should keep the root system healthy. Usually, it is enough providing the well-draining soil for your plant.