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.



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!


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.