by Lydia Holley August 9, 2021
Mexican Petunia, Ruellia simplex, bears purple blooms on four-foot tall stems. In the north, it is used as an annual, but here in zone 8, it is considered a perennial. It likes full sun and is heat tolerant. Most plants will go dormant or suffer in summer when nights stay warm, but Mexican petunia continues to grow, even thrive.
Mexican petunia both self-seeds and spreads underground by rhizomes. This makes for a thick patch which is great to have if you are looking to smother weeds. However, be certain you are aware of its aggressive spreading tendencies because it is hard to get rid of entirely once it has become established.
According to Lady Bird Johnson Wildlife Center, Mexican petunia can throw seeds as far as 30 feet. It is listed on the Texas Invasives Database and is considered an invasive species in Florida. Because of that, you may wish to substitute one of the Texas native ruellias instead: Ruellia drummondiana, Ruellia humilis, Ruellia metziae, Ruellia nudiflora, or Ruellia occidentalis.
Drummond’s Ruellia, Ruellia drummondiana, is the host plant for the Common Buckeye butterfly and will grow in shade. Fringeleaf wild petunia, Ruellia humilis, flowers in a light violet and grows to only around two feet tall. It, too, is the larval host plant for the Common Buckeye.
White Ruellia, Ruellia metziae,is shorter still, only around one foot tall, and as its common name suggests, blooms are pure white. Violet Ruellia, Ruellia nudiflora, looks the closest to Ruellia simplex, but the native plant is the host to four types of butterflies. Western wild petunia, Ruellia occidentalis rounds out the native Texas Ruellias. These are not always easy to find for sale, but are worth looking for.
If you can get by with a shorter version, there is also dwarf Mexican petunias which do not spread as aggressively as the taller version, although they do throw out seeds. The dwarf Ruellias are just as easy to grow as their taller cousins, and are listed as a Texas Superstar.
’Katie Blue’ is the most commonly found cultivar of dwarf Mexican petunias. The name is a bit misleading, since it is more purple than blue. Still, this color blends well with many other plants and color schemes. There is also ‘Katie’s Pink’, which, of course, blooms pink. Dwarf Ruellias only grow to around six inches tall. They will lose their leaves in winter, and are slow to emerge in spring.
If you are looking for a Ruellia but are concerned about the reputation Mexican petunias have of escaping their boundaries, consider getting either a dwarf cultivar or one of the Texas natives. Not only will you enjoy them; the butterflies will, too.
For more information, call 903-675-6130, email hendersonCMGA@gmail.com.
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