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Ruellia Thrives In Mississippi Summers
By Norman Winter
Central Mississippi Research & Extension Center
Few plants are as tough and more deserving a place in the Mississippi flower border than the Ruellia (Ruellia brittoniana). Not only does it endure high heat and humidity, but it is also a performer in drought-like conditions. This may be very important if the second half of the El Nino prediction comes through. That prediction calls for very little rain this summer.
Though called the Mexican petunia, Ruellia is not related to petunias. Petunias are in the family solanaceae, giving them relatives of tomatoes, peppers and eggplant, while the Ruellia is in the acanthaceae with family members like the thunbergia or black-eyed Susan vine.
Ruellia has bluish-purple flowers that radiate color from the plant. This one is usually not sold by varietal name in our area. There are also pink flowered varieties available like the Chi-Chi Pink that reaches 36 to 48 inches in height and has a spread of 18 inches. I am partial to the taller varieties that are well suited to the back of the perennial border. Shorter varieties, like Katy's Dwarf, are available that only reach 8 to 12 inches and spread 12 to 24 inches.
Ruellia grows best in full sun, but I have seen some remarkable plantings on Midway Road south of Jackson that receive quite a bit of shade and still bloom profusely. The Mexican petunia thrives in moist well-drained organic rich soils and performs well in poorer soils, too! A word of warning: in the highly rich soils, it can spread if you don't pay close attention. If you hate plants that might become invasive, then choose Katy's Dwarf.
The deep green foliage with hints of burgundy is attractive and works well in combination plantings. The leaves are narrow, pointed and reach almost a foot in length on large varieties. The flowers are borne in clusters on forked branches. The flowers are tubular or funnel shaped and may reach two inches in length. The long bloom period is usually between June and October.
I love them planted with lantanas like New Gold, Pink Caprice, Tailing White and Silver Mound. Other good combinations are Ruellia and purple cone flowers, like this year's Perennial Plant of the Year (Magnus) or my personal favorite, Bravado uellias. Ruellia also works well with our old-fashioned summer phlox or garden phlox, pentas and verbenas.
Besides being an asset in the perennial border, ruellias definitely shine when planted as a mass or as accent plantings. They are both larval and nectar sources for butterflies, but I have not witnessed that for myself yet.
The ruellias that will be for sale at your nursery later this spring are definitely perennial in zone 8, and people have told me they return in northern Mississippi in zone 7 with a good layer of mulch for winter protection.
They are also easy to propagate. You can divide clumps, root cuttings and plant by seed. Stems are easy to root in moist soil or sand. Another big plus is that they are disease and pest free unless I coax a butterfly's offspring to munch on one.