Original Post Date 5/25/2011
In my opinion, the perfect border plant is Dwarf Mexican Petunia or Ruellia brittoniana. Although originating from Mexico and unlike the “south of the border” pun in my title, Dwarf Mexican Petunia is hardy in the United States up through Zone 8 and depending on seasonal low temps, is a tender perennial through Zone 7. You might even see it come back in Zone 6 if you mulch and protect it through winter.
Dwarf Mexican Petunia is a low growing, clumping plant with lance-shaped dark green leaves that in the summertime produces vibrant violet, pastel pink or snow white flowers depending on the variety. The greenery of Dwarf Mexican Petunia reminds me of the clean lines of typical low growing, edging plants such as liriope and mondo grass, but it has the added bonus of creating beautiful blooms! Speaking of blooms, although its flowers are tubular and very similar in shape and size to a pentunia’s, interestingly, Ruellia brittoniana is not related to the petunia family. Instead, it is of the Acanthaceae family, which oddly also includes the shrimp plant and black-eyed Susan vine.
For many years, I have had violet Dwarf Mexican Petunia planted as edging along my large flower bed in the back yard. It has been extremely dependable as a perennial in my area of Zone 8. It enjoys full sun but will tolerate part shade, although the more sun it receives the more it will bloom. Dwarf Mexican Petunia is drought tolerant and I have actually seen it referred to as a desert plant, however, all agree it does best if it receives water on a regular basis. Since making my first purchase of a few plants several years ago that I widely scattered around the perimeter of my flower bed, I have not had to make another purchase although I now have a thick, healthy continuous row of them. This is because Dwarf Mexican Petunia not only returns more vigorously every year, it dependably re-seeds and oftentimes produces, what I call, “babies” every year through rhizomes. When you find a new plant or two (or three or four) developing outside of your planting area, simply dig them up with a spade and move them to any desired spot as Dwarf Mexican Petunia transplants very well. In fact, if a bare spot develops in one of my patio planters, I usually place a Dwarf Mexican Petunia seedling in the space as it is a great blooming filler plant and its leaves drape over the sides of containers very elegantly.
As I mentioned above, after the first year of planting you will surely find new Dwarf Mexican Petunia plants growing outside of your designated area. Believe me, you will sometimes find them far from your original planting area! Late one fall afternoon several years ago, I actually witnessed the reason I find little plants growing in my sidewalk crevices, across the patio, and some, deep into the back yard. As I typically do after work, I had walked onto the patio to admire how my garden was growing (most likely with a glass of Pinot Noir) when I heard this continuous popping noise. It sounded like when you first pour milk onto your Rice Crispies cereal. The noise was incredibly puzzling to me and I was bound and determined to find its source. I suspected some odd, destructive bug had probably invaded my flower bed, but upon closer look there was no sign of any type of grasshopper, cricket or otherwise. As I leaned even closer to the soil, I was able to conclude the noise was indeed originating at ground level, but still, I could see no obvious cause. I then decided to lie down on the ground and focus intently on watching my flower bed. (I said I was determined.) As I lay there for a while, I actually witnessed a seed pod from a Dwarf Mexican Petunia pop wide open and literally spit about a dozen seeds in the air and onto the patio! What I had been hearing was the pods popping open and the seeds landing on my concrete patio. It was quite a sight and certainly reinforced to me that plants are indeed extraordinary living things and their interesting growing behaviors have purpose!
In conclusion, if you’d like to add a nice border to your beds and/or insert a little texture to your containers, I urge you to purchase a few Dwarf Mexican Petunias and give them a try. If you already have some, dig up a few “babies” that are surely sprouting up these days and share their beauty with your family and friends.
Side note: I’d like to mention there exists a non-dwarf Mexican Petunia as well. It is also a gorgeous plant that tolerates the same conditions as the dwarf variety. It is less dense in foliage and stands about 2.5 – 3 feet tall and thus, is not appropriate as a border plant. If you are specifically looking for Mexican Petunia as a nice edging plant, be sure to read the tag and note that you are purchasing the dwarf variety.
Until next time-
Update: If you wish to grow from seed, I will be happy to send some to you as I collect them this upcoming fall (Sept/Oct 2015). Please send your name and address via comment or email (I will not publish) and I’ll be happy to send some your way. They are extremely easy to grow from seed and you’ll love the results, I promise! The only thing I can’t promise is the color of the bloom as I have white mixed with blue at this “new” residence, but blue will be the dominant color.