One More Summer Sizzler — Mexican Petunia

July 13, 2012 | By | Comments (12)

Ruellia 001_phixr When you see a plant blooming its head off in a strip of compacted dirt between a parking lot and concrete wall in rainless, nasty July, you know it’s a tough customer. That’s just one of the reasons people love Mexican petunia.

As its name implies, Mexican petunia comes from south of the border. (No, I’m not talking about that tacky tourist park on the NC/SC line where Pedro sells sombreros the size of beach umbrellas.) Mexican petunia is not a real petunia, but its flower looks like one. The accepted botanical name is Ruellia brittoniana, but you’ll also see it called R. malacosperma and R. tweediana. Some folks say these are different plants and others say they’re all the same one. Grumpy says, “Who the h*** cares?” I mean, really. We’re busy people.

Cold-hardy in UDSA Zone 7 and southward, Mexican petunia grows 3 to 4 feet tall with attractive, purplish stems and narrow, lance-shaped leaves. Showy blue or purple flowers, beloved by butterflies and hummingbirds, appear from early summer through the fall. How showy are they? Well, when you find pots and pots of Mexican petunias in bloom in front of Home Depot and Lowe’s, you know know even non-gardeners find them fetching.

The Good, the Bad, and the Pretty

First, the good. Mexican petunia is incredibly easy to grow in full to partial sun. It’s one of the few perennials Grumpy knows that grows equally well in wet soil and dry soil. I often see it thriving in traffic islands, gas station plantings, and strips between sidewalks and curb where it gets absolutely no care. And as I mentioned before, butterflies and hummers covet it. Individual flowers last but one day, but there are always new flowers opening.

Now, the bad. The fact that this plant is a survivor means it can get out of hand. It forms large clumps by spreading roots that are hard to kill. And its exploding seed capsules scatter seed far and wide. In wet climates and unmanaged areas, it can be invasive. Indeed, the state of Florida considers it as such, although I hardly think it ranks up there with kudzu, popcorn tree, privet, and water hyacinth.

So should you still plant it? Yes, as long as you plant types that are not invasive. Fortunately, Grumpy knows of a few that are now available in garden centers and mail-order nurseries.

Here’s the first one. It’s a dwarf called ‘Katie.’ It grows about 10 inches high and 12 inches wide. It sets few seeds and is not an aggressive spreader. Large, blue-purple flowers appear from June until frost. This is a good one for massing as a ground cover. Niche Gardens is a good mail-order source.

A second Mexican petunia to consider is ‘Purple Showers.’ It looks a lot like the plant pictured up top, but has larger, deep purple flowers. Developed by the University of Florida, ‘Purple Showers’ is sterile, so it sets no seed. However, it still can spread by roots, so don’t plant it in wet soil. You can order this one from Avant Gardens. It’s also available at big-box stores.

Nruellia2 copy_phixr
Your third choice is to go native and plant a charming little species indigenous to the Midwest and South called Carolina wild petunia (R. caroliniensis), pictured above in my garden. It grows only a foot tall and blooms off and on all summer. It will spread by seed some, but not enough to be annoying. And it’s just as tough as Mexican petunia. I got mine from Jean in Tennessee, who’s a wonderful person despite being a die-hard Volunteer fan (Oh, the shame!). You can order it from Woodlanders. It does well for me in sun and light shade and is more cold-hardy than its Mexican cousin.

Don’t Forget the Tomato Contest!

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Grumpy’s Big Fat Tomato Contest

I know it’s been a tough summer for growing tomatoes, but Grumpy believes in you! So be sure to enter Grumpy’s Big Fat Tomato Contest before August 31. Prizes will be awarded for:

  • Biggest Tomato
  • Prettiest Tomato
  • Weirdest Tomato
  • Mr. Tomato Head

It’s your chance to achieve tomato immortality. Click here for instructions.


  1. Friends don’t Give Friends Mexican Petunias – The Hairy Toe Gardener

    […] forward to the here and now, I would never in a million years plant tall Mexican petunias nor would I ever offer them to a friend, and yes, they grow in east Texas […]

    May 17, 2017 at 12:09 pm
  2. Sharon White

    When do Mexican Petunias start to come up? Mine looks dead. I live in zone 7. It’s April.

    April 10, 2017 at 9:04 am
  3. JoLene

    If theses are aggressive which is strongest crape Myrtle or Mexican petuina

    July 19, 2016 at 5:23 pm
  4. Jessica

    I have a bed of Mexican petunias quarantined between 2 walls of my house & a walk-way to keep it from invading badly. This bed has been beautiful for years and years. But this summer it isn’t blooming. I water & fertilize, but nothing but a few blooms. Not the sea of purple from years past. What could be the problem?

    June 27, 2016 at 3:25 pm
  5. The School Garden, in late winter – newsprung

    […] in an optimistic mood, we planted cannas and Mexican petunias along the fence line. Both should split and spread and make a nice curtain between the garden […]

    March 9, 2016 at 4:50 pm
  6. Sharon Cotton

    My Mexican Petunia is not blooming this second year and it is potted, also the gift I gave my daughter-in-law’s has stopped blooming?

    August 14, 2015 at 9:33 pm
  7. Garden Designs With Mexican Petunias Plant | bestgardentrellis

    […] One More Summer Sizzler — Mexican Petunia | Your Hub for … – … when you find pots and pots of Mexican petunias in bloom … pictured above in my garden. … but I have been calling it Mexican Petunia. A single plant popped up …… […]

    August 14, 2014 at 10:06 am
  8. Maria gillespie

    Pot in a container

    May 2, 2013 at 5:14 pm
  9. Jean

    P.S. ever try pulling one of those little wild petunias out of the ground? You cant!

    July 14, 2012 at 10:51 am
  10. Jean

    You have wounded me to the core! There is no UT orange evah in my world! Glad the little transplants are well and happy there in Auburn Land even tho they are dyed in the wool BAMA flowers! Maybe they can make some converts!

    July 14, 2012 at 10:50 am
  11. ck

    Thanks for clearing that up. I have the Carolina petunia growing freely in my yard, but I have been calling it Mexican Petunia. A single plant popped up in my garden in St Louis and no one could identify it. I moved it with me to Alabama 15 years ago and let it go native. That and the charming Herb Robert have free run of the garden.

    July 14, 2012 at 1:28 am
  12. Danielle

    A lot of folks here in Florida don’t like these because they are too invasive…but I really love them!! They are very dependable and can fill up a space in no time.

    July 13, 2012 at 5:42 pm

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