Ruellia

( roo - ELL - ee - uh )

At-A-Glance Information

This genus includes evergreen shrubs and shrubby perennials, and needs full sun to light shade to perform well. Water needs vary, depending on the species. See the species descriptions below for more watering information. Ruellia flowers are bell-shaped and vary in color, and are commonly called Mexican Petunias or Wild Petunias, due to their flower shape (they are actually not very closely related to Petunias, but their flowers do look similar). Use these popular ornamentals in mixed beds, window boxes, or to line walkways. 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). 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. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Ruellia brevifolia (Tropical Wild Petunia, Red Christmas Pride)
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. Spreading, bushy habit.

Ruellia brittoniana
This shrubby perennial plant grows well in zones 8, 9, 12-24, H1 and H2 and is native to Mexico. It reaches 3 feet tall and 1.5 feet wide, but will spread rapidly if unchecked. It is considered to be invasive. Leaves are narrow and dark green, and flowers are lavender-blue, appearing during the warmer months of the year. Varieties include 'Chi Chi' (with soft pink flowers), 'Katie' (a dwarf - 10-12 inch tall - variety that is non-invasive), 'Blanca' (with white flowers), and 'Rosa' (with pink flowers). This species requires regular waterings for best performance and flowering.

Ruellia californica (Rama Parda, Flor del Campo)
This species takes the form of a shrub, and grows well in zones 12 and 13. It is native to the Sonoran Desert in Mexico, and reaches 2-4.5 feet tall and wide. 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 'Ragin' Cajun'
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.

Ruellia geminiflora (Ipecacuanha-da-Flor-Roxa)
Native to Argentina, Brazil, the Guianas, and Venezuela, these shrubby plants produce green foliage and light purple flowers.

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.

Ruellia macrantha (Christmas Pride)
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.

​Ruellia peninsularis
This shrub Ruellia species is best in 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.

Ruellia tuberosa (Minnieroot, Fever Root, Snapdragon Root, Sheep Potato, Popping Pod, Duppy Gun, Cracker Plant)
These plants grow from tuberous roots, and produce lavender to violet-colored tubular flowers. The dry pods that follow flowers pop open when rubbed with water. These plants prefer moist, shaded environments, though they grow well in disturbed soils in full sun as well.

Caring for and pruning Ruellia shrubs

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, perfect for cottage or natural-looking landscapes. Plant 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. Keep soil consistently moist during the active growing seasons in spring and summertime, and lessen waterings when the plant is dormant in late fall and winter. Established plants are considered to be somewhat drought-tolerant, but regular waterings will encourage better flowering. Apply a layer of organic mulch around the base of the shrub to increase soil moisture retention and suppress weed growth.

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. Fertilizing is not generally required for these shrubs, but if they seem to be struggling or not flowering well, they may benefit from a feeding of a balanced, slow-release fertilizer in spring and early summertime to support healthy growth and flowering. These shrubs will die back in areas with cold winters. Plants can either be protected from cold temperatures, or if they are growing in a container, they can be physically moved indoors during the cooler months of the year.

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
  1. 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. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. 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.
  3. 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.
  4. 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
  1. 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. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
  2. 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.
  3. 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.
  4. 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 (any kind will do, though it does need to be well-draining), compost, and pots (12 inch pots will do, and these are 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:
  1. 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.
  2. Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick tuberous section.
  3. 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.
  4. 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.
The seed pods on Ruellia shrubs are left behind after flowers have faded, and will begin to open up when seeds are ready to be dispersed.
Ruellia seeds.

Problems and Pests

Although Ruellia shrubs are generally resistant to pests and diseases, they can have issues with the following:
  • Aphids
  • Whiteflies
For information on these garden pests, including how to eradicate them, see the following links:
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Gallery

Great for border plantings, these shrubs really put on a show when they are flowering.
Use Ruellia shrubs as screening plants, or to hide eyesores in the landscape.
Butterflies will be drawn to these flowers in your garden.

Videos

All about Mexican Petunia shrubs.
How to grow and care for Ruellia shrubs.
Learn more about these beautiful flowering shrubs.
How to trim and prune Mexican Petunia plants grown as low shrubs.

Resources

Mexican Petunia Care (Watering, Fertilize, Pruning and Propagation)
Mexican Petunias: Plant Care and Growing Guide
Ruellia
How to Grow and Care for Ruellia
Wikipedia: Ruellia
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 580, Ruellia
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