Yes, it spreads rapidly by seed and rhizomes in warm climates.

Can I grow it in a pot?

It grows very well in containers, which also helps contain its spread.

Plant guide

Mexican petunia.

Ruellia simplex

Pronounced roo-EL-ee-uh SIM-pleks

Also known as Britton's Wild Petunia, Mexican Ruellia, Mexican blue-bells, Mexican bluebell, Mexican petunia, Softseed wild petunia, Spanish-ladies

Mexican Ruellia — Photo by Greg III Espera (CC BY) via iNaturalist

The Mexican petunia is a tough, fast growing perennial that brings a splash of color to your garden. It is quite adaptable and thrives in many different conditions. You will love how easily it spreads to fill in empty spots.

Another photo of Mexican petunia — Photo by Josiah Londerée (CC BY) via gbif

At a glance

Care level: Easy
Plant type: Perennial
Light: Full sun to partial shade
Indoor light: Direct sun
Water: Every 3 to 7 days
Mature size: 3 to 4 feet
Growth rate: Fast
Hardiness: USDA 8 to 11
Bloom time: Late spring to early fall

Care

Keep the soil consistently moist to help this plant bloom its best. Watch for wilting leaves, which indicate the plant needs a drink. It is a vigorous grower, so keep an eye on it if you are planting it in the ground.

Watering: Water whenever the top inch of soil feels dry to the touch.
Feeding: Apply a balanced liquid fertilizer every two months during the growing season.
Pruning: Trim back the stems after flowering to encourage a bushier shape and more blooms.
Repotting: Move to a larger container once the roots begin to circle the bottom of the pot.
Soil: Well draining loamy soil
Soil pH: 6.0 to 8.0
Temperature: -7 to 38°C
Humidity: 40 to 80%
Drought tolerance: High
Lifespan: Perennial, typically 3 to 5 years.
Deer and rabbits: High

Signs it needs repotting

Roots growing out of drainage holes
Water running straight through the soil
Stunted growth

Safety

People: It is generally considered non-toxic, but ingestion is not recommended.
Pets: This plant is generally considered non toxic to cats and dogs.
Children: The small, dry seed pods could pose a minor choking hazard if ingested by small children.
Contact allergens: No notable skin irritation is associated with this plant.
Airborne allergens: Pollen may cause mild reactions in sensitive individuals during peak bloom.
Edibility: This plant is not considered edible and should not be consumed.

How to identify it

Lance shaped dark green leaves
Trumpet shaped purple or blue flowers
Slender upright stems
Veined foliage texture

Height: 0.6 to 1.2m
Spread: 0.6 to 0.9m
Leaves: dark green, purple-tinged, evergreen
Flowers: violet, blue, white, pink, 3 to 5cm
Fruit: brown, late summer

Problems to watch for

Spider MitesCommon
ChlorosisUncommon
Leaf SpotUncommon
Root RotUncommon

By symptom

Plant problems by symptom

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Growing it

Propagation: seed, division, cuttings
When to plant: spring, early summer
Overwintering: In colder areas, cut the foliage back to the ground after the first frost. Mulch the base to protect the roots from deep freezes.
In containers: It is excellent for containers, but use a pot at least 30 centimeters wide to accommodate its root system.

Stem cuttings

Take a 10 centimeter cutting in summer.
Remove the lower leaves.
Place in moist soil until rooted.

Plant in containers if you want to prevent it from taking over your garden beds.

Grows well with

Lantana · They share similar water and sun requirements.
Salvia · Both attract similar pollinators to the garden.

Similar species

Wild Petunia · A smaller, native alternative that is less aggressive.

Science

Family: Acanthaceae
Genus: Ruellia
Order: Lamiales
Class: Magnoliopsida
Native range: Mexico, the Caribbean, and South America.
Conservation: It is considered invasive in several southern states due to its aggressive self-seeding nature.

It colonizes wetlands and disturbed areas by rapidly dispersing seeds through explosive dehiscence.

Value to wildlife: nectar source, larval host plant
Pollinators: bees, butterflies, moths
Uses: pollinator gardens, border plantings, container gardening

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 7/9
Temperature: 8/9
Moisture: 6/9
Nutrients: 5/9

Taxonomy resolved against GBIF.

Questions people ask

Is it invasive?: Yes, it spreads rapidly by seed and rhizomes in warm climates.
Can I grow it in a pot?: It grows very well in containers, which also helps contain its spread.

Where the name comes from

The genus honors French botanist Jean de la Ruelle, while simplex refers to its simple, unbranched stems.

Good to know

It is often called Mexican petunia despite not being a true petunia.
The flowers typically last only one day before dropping.
It thrives in both standing water and dry soil.

Also in

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This guide was generated with AI on September 26, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.