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The Plant Guide

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Mexican petunia

Ruellia brittoniana 'Purple Showers'

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This three-foot-tall evergreen shrub bears many tubular, blue or purple, petunia-like flowers on dark stems over a long period. Each flower lasts for just one day. It is a fast grower that may self-seed aggressively. Use in a border, container, or at waterside. Can be grown as an annual in cooler areas.

Noteworthy CharacteristicsPetunia-like flowers from spring to frost. Native to Mexico and the southwestern U.S.             

CareRuellia needs a warm climate. Site in partial shade and fertile, consistently moist, but well-drained soil.

PropagationSeed or softwood cuttings in spring. Self-sows aggressively if conditions are right.

ProblemsNothing serious.

  • Genus : Ruellia
  • Plant Height : 1 to 3 feet
  • Plant Width : 1 to 3 feet
  • Zones : 10, 11, 8, 9
  • Uses : Containers
  • Bloom Time : Early Fall, Early Summer, Late Spring, Late Summer, Summer
  • Growth Rate : Fast
  • Light : Full Sun to Partial Shade
  • Moisture : Medium to Wet
  • Maintenance : Moderate
  • Plant Type : Perennials
  • Plant Seasonal Interest : Spring Interest
View Comments


  1. suebanos 06/23/2014

    I just bought one at a nursery but was told it was an annual.....

    1. user-7007147 08/15/2014

      I was given a piece of this several years ago and now it is everywhere. I love it, it comes back each year bigger and better.

    2. carolfaulkner 08/30/2014

      Depends where you live. Zone 8 or 10

    3. user-7008311 11/18/2016

      it is in colder zones.

  2. crissyyoung 08/28/2014

    Can horses eat this plant? Our bush is crazy big. I need to trim in it.

    1. walter_moser 08/23/2015

      Bush? Whatever you have is not a MEXICAN petunia, they grow in single stems???

      1. elizabeth40 05/17/2017

        BUT DON'T MOST BUSHES HAVE A SINGLE STEM, or trunk, if you prefer that term, THAT PUTS OUT BRANCHES? it's just a term, don't get your panties all wadded up about a word

  3. carolfaulkner 08/30/2014

    I am in Dallas. Love this plant which survived our winter. It is an aggressive plant but worth it since it has has continual flowers. I have a purple and pink. Carol

  4. patheninger 09/05/2014

    Just planted a couple of these last weekend and they are not doing well. they are in the sun for most of the day and the ground is still moist.

    1. user-7007752 08/07/2015

      They will do very well with morning sun and afternoon shade. We water ours once per week. We live in Austin, TX

  5. mitzieeckenfelsborders 09/30/2014

    How do I take care of this plant in the colder months? I live in KY

    1. user-7008311 11/18/2016

      Pull them out of the ground and transplant them in a pot and bring them inside
      place in a sunny spot

  6. user-7007606 05/22/2015

    Just bought my first ruellia tree. Live in Canada where winters are cold but summers can be very hot. I just planted it in a very sunny spot because the tag said full sun. I find it drooping in the sun, and perking up in the shade. Not sure if it's because it's has a bit of transplanting issues. Or should I just be replanting it somewhere shady.

    1. user-7008260 09/30/2016

      Depending on who you buy from, the tags can say different things. So I always Google it first. This one says Sun to Part Shade. Had the same experience with a Royal Robe Potatoe Bush. Must also consider temperature. It can be over 100 most of the summer where I live, then there is a month where it can be in the teens in winter. So experiment and use the tags as a suggestion.

      1. riverp 05/18/2017

        Yes exactly the sun is hotter, more intense, higher UV in some areas than others so one set of instructions isn't going to ever cover everything.
        With these though the thing is they flower better with as much light as possible short of wilting. So it's that threshold you have to accommodate wherever you 're gardening. Wet soils are a must unless you are happy to water everyday. For me after my experience nice big pots with no drainage holes are the perfect place to keep them in check and only plant the sterile cultivars. Try not throw them on the compost or elsewhere if you prune because you could depending on your local climate spread a problem. We have extreme humidity and heat so they are fine in quite a lot of sun, we just avoid mid day sun. Think dry sun is more of a problem.
        They're fantastic and create a lovely light, airy, purple blueness that dances in the breeze. Those fragile, paper crepe like flowers ,dancing, backlit in morning sun are a bit of a classic for tropical gardens with our shortage of perennials. They flower in abundance but the flowers won't stay open all day and are usually gone as the day gets hotter. Certainly more morning glory than anything else and well worth it.

    2. riverp 04/14/2017

      Yea it will droop in the sun unless you water every day. Needs dappled shade, and wet feet at all times, morning sun is OK.

  7. patriciaressler 07/12/2015

    I just got one of these plants and I want to bring it into the house in the fall. I was wondering if anyone could tell me if it could be poisoness to cats

  8. Art_4u 07/12/2015

    If I don't water this plant every single day it droops.

    1. riverp 04/14/2017

      Understatement! It grows particularly well in boggy soil, as a pond marginal. In a pot its a nightmare as it will droop and wilt if you don't water it every day. Better in a pot with no holes and a bit of shade during the hottest time of the day.

  9. user-7007850 10/12/2015

    i love this plant... It spreads and is beautiful...It has to be watered here in Louisiana. and watered a lot ...it is worth it...

    1. user-7008225 08/21/2016

      We bought two at HP a year and a half ago. They grew like saturn rockets, and got untidy/huge. So we dug them up and planted something else in their place. I took a broken branch, and put it in another flower bed. It rooted, and grew just as fast. I have trimmed it back several times, but it is still over 6 feet tall.
      Now the bed for the dug-out two is sprouting shoots constantly. They appear to grow about 3 inches PER DAY! We call it our "Frankenplant". It appears to grow incredibly fast, and puts out sub-surface runners in all directions - a long distance from the original plants. We have tried digging out the runners, roundup and a variety of other inhibition strategies. None work. No wonder it is an "invasive species".
      Beautiful flowers. Maybe we can train it to eat kudzu... But otherwise it is only a matter of time before it takes over our yard (and then the state of California?).

      1. Newsie3 03/20/2017


      2. elizabeth40 05/17/2017

        That is a true example of how it grows in florida.... I didn't know cudzu had spread all the way to cal. Ruella is in line to take over huge areas....

    2. riverp 04/14/2017

      Yea me too. Its the purple blue colour and etherial flowers that go on and on masses of them. It needs a bit of shade from midday sun. Its a chronic pest in some areas as it self seeds liberally. I have a taller one, five foot or so, dark purple, black stems, it's completely sterile so it behaves OK. Previously I had a short one just a few feet tall, complete nightmare, white, pink and purple. Seedlings used to pop up absolutely everywhere, in pots in the garden, between payvers, even one in a tree. I spent one summer pulling every single seedling I could find. Its as well that I did because when established they also grow from runners under the ground which easily break when you pull them making it very difficult to eradicate. Even though i did this I still found one or two new seedlings every year for about three years. Now its gone.

      1. elizabeth40 05/17/2017

        good for you!!!!! didn't know they had come out with a sterile variety, but I still hate them for their ancestry

        1. riverp 05/19/2017

          Yes, however for me it was trial and error. No one actually told me the one I have was sterile, just luck. Im not sure much has been done on this plant by way of breeding. There are a few "selections" but I think R. Simplex (syn brittonia) "Katie" and here "Purple showers" etc are just names, coined in marketing along the way. Like the white one called "paper showers", it's just intermediate in height and white, otherwise not sterile or much different from any others. All seem to happily self seed except the very tall black stemmed one I have kept. Basically the same as "purple showers", tall, black stems with purple/blue flowers. I found it by chance in a market in China and was informed it came via Thailand. I also saw something very similar growing along a road side in Phnom Penh, Cambodia. There were no obvious seedlings in sight so perhaps that one was also sterile. I never found one in America that was sterile. I would've destroyed mine already if it wasn't sterile so maybe it's my own selection on "purple showers" as purple showers itself is certainly not sterile........haven't seen one marketed as sterile as such anywhere. LOL maybe the X-rays at customs when I flew it home made it sterile.....some gamma ray treatment. Im thinking a variegated sterile one would look lovely so have been toying with the idea of getting it subjected it to gamma rays anyway!

          1. elizabeth40 05/19/2017

            Thanks for your feed back... I think there may be a sterile variety here in florida,as I think I have seen some purple ones that don't seem to have encroached into yard and other shrubs. I don't know or care. This damned plant has taken too much of my time already. I just want it gone, and hope I never see one again.........

          2. riverp 05/20/2017

            I understand the sentiment completely.

            These species pose a very real threat to flora and fauna in many parts of the world. It probably should if it isn't already, along with things like Lantana be banned in places of the world like Florida.
            Of course its not a pest everywhere on the globe however a sterile selection would make it less so where there is even the smallest chances it could become so. The sterile one should be promoted where ever it's found. Having said as we know it's not only uncontrollably fecund in the production of fertile seed but spreads rather too successfully by those runners. Florida and maybe the Southern States I would think Ruellia simplex paradise. All that perfect swampy warm dappled shade.

            The sterile one I have seems less of a runner too. I grow them in very big water pots anyway but they happily sit dead centre hardly expanding at all, so that I have a nice tiny leaf ground cover right around the base of the stems. With this one I cut all the stems down to about six inches once a year after the dry season and they shoot from the old stems. Once a year or so it manages to throw out a single big thick soft side runner which I just pull up gently back to the main clump and cut. That seems to be enough to put it off doing much more each year. It flowers very well and profusely and the flowers are a nice inky saturated purple/blue.

            So it's sterile and a slow spreader.

            The other one would self seed and run all at once without a breath even if it wasn't flowering it would be running madly. Not very tall, it also didn't flower so well, tending to throw up single random flowers but always enough to produce hundreds of those seedlings. Pale pink, white and blue/purple. So very definitely a good and bad guy lurking in the genus here.

            I would love a white as well behaved as the other......

            I know someone who grows it in Greece, the "lethal" one where it behaves extremely well, they have winter rain and long hot dry summers so the seed doesn't get to germinate as it's a summer (wet season) grower and nor does it run about as the surrounding ground is generally too hard and dry in summer. It grows only where its looked after, like at the base of a dripping tap. It also flowers extremely well. So I should think quite suitable for warmer parts of places like California.......

            I bought a sterile white Lantana, extraordinarily handsome plant, it embodies (as much as a plant can) sophistication, luxury and charm. Covered with crisp, big, bright white clusters of flowers just touched by gold, set in deep deep glossy green leaves. However this winter to my "horror" I noticed three of the flower clusters had produced one to two fully developed shiny black berries! These I picked planting the seed within and yes absolutely they all germinated. Im not in a Lantana frenzy just yet. The plant is not a problem here like it was where I lived previously. I want to see what these plants turn out to produce flower wise. But it does just show......

  10. TQTQ 05/13/2016

    This plant is so invasive and aggressive, I regret the day my friend gave me ONE stem 14 years ago. I've tried every thing and spent so much money trying to get it out of my yard in Houston.

    1. elizabeth40 05/17/2017

      I too, regret ever planting this evil plant.Where it spread all through my floritam lawn, I have finally resigned to have to resod someday, so I just poison it with straight concentrated poison, on a very regular basis. Perhaps some day, it wiill go away.... the DEVIL PLANT

      1. matt_dorsey 05/25/2017

        So I should Not get one of these for the front garden area ?

        1. elizabeth40 05/25/2017

          I f you live ,like me, in central florida, east coast, it never freezes. People further north seem to have them freeze out every year. But I never water them, except for when my yard gets sprinkled, @ 2 times per week at night. I strongly recommend staying away from them unless they are guaranteed sterile

  11. brittannywalker 07/21/2016

    I planted two Ruellia a few weeks ago. At first, one was doing very well and not the other – now, the one that wasn't doing well is thriving and the one that was doing well is not. Do any of you know why this may be happening. They both get the same amount of water and sunlight but they are in two different flower beds. And thoughts?

    1. user-7008260 09/30/2016

      They need acidic soil, use azalea mix

  12. bettyosbornejohnwillard 10/08/2016

    Have a pretty good sized plant and would like to set some out in another area of our yard. How do I transplant a couple ?

  13. user-7008405 03/12/2017

    A couple stalks of the purple "Mexican petunia" sneaked under our backyard fence from the neighbor's garden about two years ago (Orlando, FL). I clipped and rooted them. They both have grown into multi-stalked 3-foot and 4-foot BUSHES, and both have sent out dozens of runners. I had no problem letting them fill up an otherwise bland section of the yard. Whenever they spread too thickly, I simply mow them with the grass. They are common yard plants in this part of the country.

    1. henrycasado 09/10/2017

      Im new to planting , and I have this plant now,"Mexican petunia" how do you go about rooting it and what did you use . thanks

  14. user-7008507 04/28/2017

    are flowers free? My grandma just died.

  15. jacquelinedecorte 06/22/2017

    can I trim these flowers down without hurting them?

  16. user-7008968 10/28/2017

    is this plant poisonous to equine ??

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