A “temperennial” here in zone 6, Tall Mexican Petunia won’t winter over outdoors for us, but it certainly will in zones 8-10. Still, we always make room for it in our gardens and also use it in container combinations where the tall 3-4′ purple stalks are clothed with narrow dark green purple tinted foliage. The continuous display of violet blue funnel shaped flowers extend on short stems from the leaf axils, and attract bees, butterflies and hummingbirds.
Ruellia ‘Purple Showers’ does enjoy evenly moist soil, and will even grow well along a pond?s edge or in low standing water, a situation that can be challenging. This does not mean it won?t grow in average soil conditions, for it will, but it does not want to fry. Southern nursery catalogs list Ruellia as an evergreen shrub. We suspect Ruellia may become territorial in warm climates, and should be planted where its vigor is an asset.