How to Plant and Grow Dwarf Bluebell (Ruellia brittoniana)


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Purple flower dwarf bluebell growing by a pond
Tubular, purple flowers are very attractive to bees and other important pollinators.

Also known as Mexican petunia or dwarf blue, dwarf bluebell belongs to the Acanthaceae family. Over 2,500 species are contained within this family, with the majority of them belonging to moist rainforest habitats, though some can be found in wetlands as well as dry upland forests.

Dwarf bluebells do best in either damp soils or in emergent water habitats, including wetlands and the edges of ponds and streams.

Sometimes, the Latin name for this plant is written as Ruellia simplex, which was the original name given to this plant when it was discovered in Cuba in 1870. Ruellia simplex should be used to reference the full-sized versions of Mexican petunia, and not the dwarf variety.

Facts, Benefits & Uses of Dwarf Bluebell

Field of dwarf bluebell growing near a lake
Alejandro Bayer Tamayo from Armenia, Colombia / CC BY-SA

 

Native to Mexico, this attractive perennial has gained a great deal of attention as both a terrestrial garden plant and a semi-aquatic water garden/pond plant due to its ease of care and attractive flowers.

Outside of Mexico, this plant is considered to be an aggressive invasive species, and as such extreme care should be taken when planting it. First and foremost, make sure that it’s legal to have in your area.

Dwarf bluebell’s large, trumpet-shaped, bright flowers draw in all manner of pollinators, including bees and butterflies. Butterflies and moths of the subfamily Nymphalinae often use the leaves of Ruellia species to house and feed their larvae.

The rhizomatous roots (also called runners) are excellent at soaking up pollutants and excess nutrients, thus improving both soil and water quality.

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Dwarf Bluebell Fact Sheet:
PLANT TYPE
Herbaceous Perennial
HARDINESS ZONES
USDA 8 – 11
LIGHT REQUIREMENTS
Full sun to partial shade
BLOOM COLOR
Blue, purple
BLOOM PERIOD
June – September (Summer to early Fall)
MAXIMUM GROWTH
Height 15 – 30 cm (6 – 12 in), spread 20 – 30 cm (8 – 12 in)
PLANTING DEPTH
.6 – 2.5 cm (.25 – 1 in)
WATER QUALITY
pH 6.1 – 7.8

Dwarf Bluebell Growth, Hardiness & Climate

Pond plants dwarf bluebell Ruella brittoniana growing beside a fish pond
gailhampshire from Cradley, Malvern, U.K / CC BY

While most Mexican petunia varieties grow up to three feet tall, this dwarf variety is lower profile and less likely to overtake areas with a maximum size of one foot tall with a possible spread up to a foot. Flowers begin to bloom in June, often lasting through September, with each bloom only living for a day before dying and dropping off of the plant.

Warmer climates are best for this plant, ideally USDA hardiness zone 8 and above. Below this, and growth may be stunted. In the U.S., coastal states are where dwarf bluebell is able to survive. If frosted, the plant will die. Either full sun or partial shade work well. Once it’s established, it’s surprisingly drought tolerant, but you should make an effort to keep soil damp if not planted directly in water.


How to Plant Dwarf Bluebell In Ponds

Dwarf bluebell with pink flower in a planting pot beside a pond
Varun Pabrai / CC BY-SA

Dwarf bluebells, and any Mexican petunia variety for that matter, should be planted in pots to control their growth and prevent them from overtaking your other plants or spreading into sensitive natural areas. Plant ¼ to 1 inch deep in soil in the pot, and place either in the ground or in a couple of inches of water along your pond’s edge.

If not planted marginally along your pond’s banks, do try to keep soil damp. Dwarf bluebells can be drought tolerant, but don’t prefer dry soils. Use aquatic soil, rather than a rocky substrate, if planting in water.


How to Care For Dwarf Bluebell

Dwarf bluebell ruellia brittoniana with purple flowers
Dwarf bluebells are incredibly easy to care for.

Again, keep their roots wet and dwarf bluebell will be happy. As it puts out aggressive runners, you’ll need to either keep these plants in pots or continually cut back their rhizomes, else they’re likely to overtake your garden and will be hard to get rid of if allowed to spread. As always, clean any pruned or fallen foliage from your pond to maintain healthy water quality.


How to Winter Dwarf Bluebell

Dwarf bluebell roots may be able to overwinter, frost will kill off any parts that are aboveground. Particularly cold winters may also kill the roots, which could prove to be a boon as it would control the spread of this plant naturally. To ensure survival, you can bring plants in during the winter, and use digging them up as an opportunity to clip and remove excess rhizomes from the ground.


Is Dwarf Bluebell Toxic, Poisonous or Invasive?

Dwarf bluebell is incredibly invasive outside of its native Mexico. However, the University of Florida is researching ways to breed and grow Ruellia brittoniana that does not produce any fruits or seeds, and therefore will not be able to spread. This would make having Mexican petunia as an ornamental plant much more feasible, and significantly less dangerous to native flora and fauna.

It should be noted that dwarf bluebell is a man-bred variety of Mexican petunia, bred to be small and less intrusive than its wild counterpart. With that in mind, theoretically dwarf bluebells are less likely to overtake areas as easily as taller, larger, and more robust varieties of Mexican petunia. Regardless, be mindful when planting so that it doesn’t spread into natural areas.

Ruellias are not known to be toxic to any animals, including dogs, cats, people, and fish, making it a safe, non-toxic plant for your pond.


Is Dwarf Bluebell Edible? Will Fish Eat it?

There is little literature on pond fish, or fish in general, eating dwarf bluebells. If they do, it would likely be the fleshy roots of the plant if planted along the shallow pond edge. Since it’s non-toxic, nibbling on the plant should not harm your fish. Most wildlife don’t seem to find it overly palatable, but some gardeners complain of deer nibbling off the flowers and tender new shoots.


Where to Buy Dwarf Bluebell Plants & Seeds? (UK & US)

A quick online search will yield you a plethora of purchasing options, from nearby plant nurseries and pond retailers to online outlets that will ship root balls and seeds directly to you. Again, please check to make sure that you can legally have dwarf bluebells in your area since it’s non-native outside of Mexico and other portions of South America.

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