Ruellia

( roo - ELL - ee - uh )

At-A-Glance Information

This genus includes evergreen shrubs and shrubby perennials that need full sun to light shade to perform well in the garden. Water needs vary depending on the species. Ruellia flowers are bell-shaped and vary in color, and are commonly called Mexican Petunias or Wild Petunias due to their flower shape. Use these popular ornamentals as a mass ground cover, to border walkways, in containers, as erosion control on sloped areas, or in pollinator, wildlife or xeric gardens. Take care when planting these shrublets in the garden, as plant parts can be toxic to humans and animals if ingested.

ruellia Species and Varietals

The genus Ruellia includes about 2,500 distinct species of flowering plants and is a member of the plant family Acanthaceae. The genus was named for herbalist and physician Jean Ruelle (1471-1537). Plants in this species are related to those in Acanthus (Bear's Breech), Fittonia (Nerve Plant) and Justicia (Shrimp Plant). Many genera of plants have been added to the Ruellia genus over the years, including Blechum, Eusiphon, Polylychnis, and Ulleria. The ideal growing zones for Ruellia vary depending on the species cultivated. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Ruellia brevifolia (Tropical Wild Petunia, Red Christmas Pride, Tropical Petunia, Red Ruellia, Short-Leaved Ruellia, Short Leaf Wild Petunia)
These plants are native to South America, and produce glossy green foliage with maroon undersides and bright orange-red tubular flowers that bloom in summertime. Plants can reach up to 24 inches tall at maturity, and grow well in partial to full shade. They have a spreading, bushy habit. Tropical Wild Petunia is suited for growing in USDA hardiness zones 9b-11 and is considered invasive in Australia, La Réunion, and Hawai'i.

Ruellia brittoniana (Mexican Petunia, Mexican Bluebell, Britton's Wild Petunia, False Petunia, Common Ruellia)
This shrubby perennial plant grows well in USDA hardiness zones 8-11 or Sunset growing zones 8, 9, 12-24, H1 and H2 and is native to Mexico. It reaches 3 feet tall and 1.5 feet wide at maturity and will spread if uncontrolled. Leaves are narrow and dark green, and flowers are lavender-blue, appearing during the warmer months of the year. Cultivars include 'Chi Chi' (to 18-24 in. with with soft pink flowers), 'Katie' (non-invasive to 10-12in. with violet or white flowers), 'Blanca' (with white flowers), 'Purple Showers' (sterile; to 3-4 feet with dark purple stems and purple-blue flowers) and 'Rosa' (with pink flowers). This species requires regular water in the landscape to thrive. It is considered invasive in the southeastern United States, eastern Mediterranean and southern Asia.

Ruellia californica (Rama Parda, Flor del Campo, Desert Ruellia, Baja Ruellia)
This species takes the form of a shrub, and grows well in USDA hardiness zones 9-11 or Sunset growing zones 12 and 13. It is native to the Sonoran Desert in Mexico, and reaches 2-4.5 feet tall and wide at maturity. Leaves are ovular and light green, and flowers are deep purple, violet or pink, appearing after summertime rains. This species does not need any formal irrigation, but will bloom almost all year round if given adequate moisture.

Ruellia elegans (Ruellia formosa) (Brazilian Petunia, Red Ruellia, Elegant Ruellia, Brazilian Red Petunia)
This variety is a perennial flowering plant that grows well in zones 4-9 and 11-24. It is native to Brazil and Chile, and reaches 4 feet tall and 8 feet wide. Flowers are scarlet-colored and bloom starting in late spring, continuing through the first frost of the season. After it is established, it needs little to moderate water. 'Ragin' Cajun' reaches up to 12 to 24 inches tall and as wide. This species is considered invasive in India, Jamaica, and Puerto Rico.

Ruellia geminiflora (Ipecacuanha-da-Flor-Roxa, Twin-Flowered Wild Petunia, Twinflower)
Native to Argentina, Brazil, the Guianas, and Venezuela, these shrubby plants produce green foliage and light purple flowers. They reach up to 2 feet tall and half as wide at maturity. This species is suited for growing in USDA hardiness zones 10-12 and is considered invasive in the southeastern United States and Hawai'i.

Ruellia humilis (Wild Petunia, Fringeleaf Wild Petunia, Hairy Petunia, Low Wild Petunia)
These plants are native to the eastern United States and are commonly grown as garden ornamentals. They typically reach about a foot tall, and have light to medium-green foliage. Flowers are lavender, and bloom in July through September, opening in the morning and falling from the plant in the evening. This species is suited for growing in USDA hardiness zones 4-8.

Ruellia macrantha (Christmas Pride, Brazilian Rose, Christmas Pride Ruellia)
These plants are commonly used as garden ornamentals, and are native to Brazil. They form broadleaf evergreen perennial plants with green foliage, and produce reddish-pink flowers in spring and summertime. At maturity, they reach up to 5 feet wide and 6 feet tall. Christmas Pride Ruellia is suited for growing in USDA hardiness zones 9-11.

Ruellia peninsularis (Desert Ruellia, Baja Ruellia, Desert Petunia)
This shrub Ruellia species is best in USDA hardiness zones 9a-11b or Sunset growing zones 12, 13 and 21-24. It is very similar to Ruellia californica in appearance and watering needs, though flowers and foliage are a bit lighter in color. Individual plants reach up to 3-5 feet tall and just as wide at maturity, forming handsome, naturally dense rounded evergreen shrubs. Flowers are purple-blue and tubular, and foliage is light green to green.

Ruellia tuberosa (Minnieroot, Fever Root, Snapdragon Root, Sheep Potato, Popping Pod, Duppy Gun, Cracker Plant, Waterkanon)
These plants grow from tuberous roots and produce lavender to violet-colored tubular flowers. The dry pods that follow flowers pop open when moistened. These plants prefer consistent irrigation and shady spots in the landscape, though they can be grown in disturbed soils in full sun as well. This species is native to the tropical Americas and grows well in USDA hardiness zones 9-11. It is considered invasive in south and southeast Asia, tropical Australia, and regions of western Africa.

Caring for Ruellia

Take care when planting these shrublets in the garden, as plant parts can be toxic to humans and animals if ingested. Plant Ruellia shrubs in full sun to partial shade; the more sun these shrubs get the better they will flower (at least 6 hours a day is ideal). In very warm climates, they can tolerate some shade during the hotter hours of the afternoon. These plants are considered low-maintenance. Plant them in well-draining soil that has been amended with plenty of organic material. Loamy soil is ideal, but they can tolerate a wide variety of soil types, preferring a pH of between 6.0 and 8.0 (slightly acidic to slightly alkaline). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, keep soil consistently moist during the active growing seasons in spring and summertime, and lessen waterings during dormancy in late fall/winter. Established plants are considered to be somewhat drought-tolerant, but regular waterings will encourage better flowering and overall performance.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. To prune Ruellia shrubs, simply remove spent flowers and trim to encourage a bushier growth habit. More extensive prunings, if necessary, should be carried out in the late spring or early summertime. These shrubs will die back to the ground over winter in non-tropical regions. In cooler climates, these plants can be treated as annuals, pulled and composted after the growing season or left in place to enrich soil and enriched in the following growing season. Plants can either be covered or they can be physically moved indoors during the cooler months of the year. Ruellia shrubs can survive for decades (10-20 years or more) in the landscape before needing to be replaced.

Propagation

Ruellia can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your shrub, follow the instructions below:

Propagating Ruellia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Ruellia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed pods are easy to find; they are left behind after flowers fade, and will dry out and turn brown when they are about ready to open. Remove these seed pods from the plant and place them in a paper bag. They will continue to open up and release seeds. Once you have gathered all of your seed pods, remove the seeds and set them aside.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Ruellia by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil, compost, and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in spring or fall. To propagate by division, follow these steps:

Gather your materials. Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the tuber roots. Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick tuberous section.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divided shrubs either in the ground or in their designated pots.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout.

Ruellia seed pods are torpedo-shaped capsules with ballistic dehiscence, meaning that mature pods snap open violently, flinging seeds away from the parent plant.

Ruellia seeds are flat and disc-shaped, typically brown to dark brown, and produce a sticky, gel-like substance when wet that helps them adhere to surfaces.

Problems and Pests

Certain Ruellia species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Although Ruellia shrubs are generally resistant to pests and diseases, they can have issues with the following: