Roger Mercer: Ruellia make pretty bedding plants

Dear Roger: If anyone knows what this plant is, I knew you would. I saw it down at the beach. It is absolutely beautiful. If you could send me some information, it would be greatly appreciated. — Teresa in Linden

Dear Teresa: This is commonly called Mexican petunia. The plants are native to Mexico, but they are not even closely related to petunias. The botanical name is Ruellia brittoniana. While the most common color is purple, the flowers can be white or many shades of purple, pink or blue-mauve.

The plants tolerate shade but grow and bloom best in full sun. The plant is a very aggressive grower and with plenty of water can take over beds of other plants. In subtropical climates, such as Florida, Mexican petunia is evergreen and listed as invasive. In the Sandhills, ruellia tends to die back to the ground each winter.

Flower colors range from white through shades of pink and purple. The most common color is purple. The flowers have little fragrance.

There are dwarf forms of ruellia, such as "Katie,'' that grow less rampantly and cause less trouble than the 3-foot, full-sized forms. Most forms of ruellia have 2-inch to 3-inch flowers. 

This is an easy plant to grow in dry or wet locations. It cannot tolerate much cold, however. Raleigh might be its northern limit for some forms, though there are reports of especially hardy forms.

Several types of butterflies use ruellias as host plants. They include the common buckeye, malachite butterfly and Australian lurcher, all recorded on several species of ruellia.

Ruellias are widely available on the internet, usually as plants but also occasionally as seeds. I would choose selected forms and buy plants.

If you’re adventurous, try seeds promising mixed colors. You might get something especially interesting. Start seeds indoors in late March and move them outdoors within a week after they have sprouted.

Transfer to pots when the second set of true leaves appears. I use foam coffee cups with holes pinched in the bottom edges. 

Move to a permanent location when plants are 6 inches tall.

Send your questions and comments to Roger at orders@mercergarden.com or call 910-424-4756.  You may message photos and text to that number. Send pest or plant samples to Roger at 6215 Maude St., Fayetteville, N.C. 28306.