Home of the Practically Perfect Pink Phlox and other native plants for pollinators

Wednesday, June 24, 2020

Wildflower Wednesday: Ruellia strepens

Ruellia strepens is offering up a bloom here and there in its less than generous fashion!

It's a pretty little flower, but, its here today and gone this evening habit, can make it less attractive to folks who are into more floriferous wildflowers. There was a time when I seriously thought of just ripping them all out, but, I have grown to enjoy the sweet lavender blue petunia like flowers that always surprise me peeking out of the greenery in the shadiest spots of my garden.

Limestone Wild Petunia is a native perennial in the Acanthus family (Acanthaceae). Not surprising that with a name like Limestone Wild Petunia it would be found growing in rich woodland soil underlain by limestone. Of course it's happy here with my 444 million year old Ordovician limestone bedrock.

It is a sparingly hairy clump-forming perennial that grows 1-3’ tall. Its strongest feature are those pale lilac to lavender petunia-like flowers (to 2” long) with five flaring lobes. If you look closely at the sweet flowers you might notice that one petal is slightly larger than the other four. This zygomorphic quality is typical to both R strepens and R humilis (another middle Tennessee native). I think of that extra large petal as a good landing pad for any pollinators that happen by.

Many of you are probably more familiar with R. humilis. I have seen it offered in several online native plant nurseries. It's very similar to our star, except, it's happier in sun and blooms throughout the hottest, driest times of the summer. I also grow it and love the Petunia like flowers.
The flowers bloom in the leaf axils; note the fine veined nectar guides

 It really is a beautiful flower. At the throat of the corolla, there are several fine veins that are purple and somewhat reticulated; they function as nectar guides for visiting insects. I think they're cool. The flowers are funnel shaped and last for one day and are strangely, easily detached if bumped against.

The fruit is a capsule that explodes open to dispel seeds

Much to my sorrow, I have never, ever seen pollinators on a blooming flower, but, I've read that long tongued bees, miner bees, carpenter bees and parasitic bees are its primary pollinators. Apparently, fertilization has been very successful in my garden, because the progeny is all over. Maybe, the pollinators are sneaking visits when I am inside. But, it's more likely as Researchers at a college in Missouri, discovered: flowers of R strepens open during the early morning dark hours, allowing pollination by moth species. That's good to know. According to another source the lavender-blue trumpets attract hummingbirds and butterflies, too. Here's a link to a site with a bee foraging on the flower! Let me tell you, I was thrilled to find it!

But, speaking of pollination. Many species within this family produce two kinds of flowers - those that have open flowers, which can be pollinated by insects, and those that don't open, which must self-pollinate. Ruellia strepens, our star, often relies on self-pollination for reproduction. Its "perfect flowers" never even open to entertain the idea of cross-pollination. Scientists call these flowers "cleistogamous," which translates as "closed marriage." (source)

I am glad it has a mechanism for self propagation, but, I would love to see some insect action!
The Particulars

Ruellia strepens
Common Names: Limestone wild petunia, wild petunia, smooth wild petunia, woodland petunia
Family: Acanthaceae 
Type: Herbaceous perennial

Native Range: Eastern United States including Texas, Oklahoma, Kansas and Nebraska
Zone: 5 to 8
Habitat: Limestone woodlands, floodplains, rich soils
Height: 1.00 to 3.00 feet Spread: 1.00 to 1.50 feet
Bloom Time: May to September
Bloom Description: Lilac to lavender
Sun: Part shade
Water: Medium
Maintenance: Low
Wildlife Value: Pollen and nectar, Leaf cutter bees have been observed cutting pieces of the corolla to use in their brood nests. They layer it in the nest, seal it up and then die. The next generation is on its own! 
Comments: The roots are fibrous and not easy to dig from dry clay soil. Genus name honors 15th–16th century French herbalist, Jean de la Ruelle.
Conservation status:

Pronunciation: Ruellia (rew-EL-ee-uh) strepens (STREH-penz)
Deer resistant



PS. It's National Pollinator Week, what better time to take this pledge. Now, please raise your hand and solemnly swear that you will never, ever, ever, ever, ever use pesticides in your garden. Now don't you feel better for having made that commitment! I know I do.

Welcome to Clay and Limestone and Wildflower Wednesday.  Thank you all for joining me as we celebrate and share our marvelous and beautiful wildflowers. I hope 2020 is the year we all plant more native wildflowers for the many critters that live in and visit our gardens. Let's be sure we celebrate them every day, not just WW. Remember, it doesn't matter if they are in bloom or not, you can still share them. Please leave a comment and add your name to Mr Linky so others can pop over to see your Wildflower Wednesday post.

Gail Eichelberger is a gardener and therapist in Middle Tennessee. She loves wildflowers and native plants and thoroughly enjoys writing about the ones she grows at Clay and Limestone. She reminds all that the words and images are the property of the author and cannot be used without written permission.


  1. What a sweet flower. I'm always game for adding some color, no matter how small, to the shady parts of the garden. As long as the voles and deer don't feast on it! Thanks for hosting Gail!

  2. It is always a lovely surprise when I am out and about to see one of these sweet petunias smiling up at me. I rarely see a cluster of flowers. It is always one purple flower standing out. I have often wondered why that is.???? I have wanted to get it going in my garden but haven't had the luck yet to find one that is available.

  3. Your URL for this post says 2015/07 ?

  4. Nice!

    I grow the R. humilis and R. caroliniensis, but was not familiar with R. strepens. I don't think I've ever seen it in offered commercially... Was it a volunteer in your garden or did you buy it somewhere?

    I agree that R. humilis seems much happier in sunnier spots. So far (first year in the garden), R. caroliniensis seems quite happy in a mostly shady spot. Both Ruellias - but especially caroliniensis - have beautiful foliage in addition to the cute petunia-style blooms! :)

  5. Knowltonia for June


"Insects are the little things that run the world." Dr. E O Wilson