It is a strangely diverse family, the Acanthus family. Several thousand years ago one of its members, known even then as the Acanthus, inspired tle most ornate of the three types of architectural columns in ancient Greece, the Corinthian with its capital designed after the curving Acanthus leaves. In the United States the family is limited in its numbers. There is the water willow with its small orchid-like flowers; the Dyschoriste of the southern pine barrens, and the Ruellia of Illinois. And here there are two Ruellias which are patterned along similar lines but grow in entirely different habitats.
Ruellia humilis Nutt.
July. Sands. dry roadsides.
Hairy ruellia is a plant of dry, open prairie. Smooth ruellia (Ruellia strepens) is a plant of moist, shady, bottomland woods. But each has the typical, opposite, oval leaves and tubular, lavender flowers which often are called wild petunias because of their similarity to that popular flower.
Hairy ruellia grows about a foot high or less and is very hairy. Its leaves are dry; the plant can withstand much heat and dryness without wilting. The flowers spring from the axils of the leaf-pairs, are blue-lavender, and last but a day. The smooth ruellia (Ruellia strepens) is a taller plant, often three feet high, with juicy, dark green, smooth leaves and stem, and pink-lavender, petunia-like flowers springing from the axils of the leaves and lasting but a day. Hairy ruellia is typical of edges of golf courses and dry banks along roads. Smooth ruellia is found in river woodlands and other moist woods with deep summer shade. Both bloom in duly.