Ruellia strepens L.

Wild Petunia


CC = 3
CW = 0
MOC = 70

© SRTurner

Family - Acanthaceae

Habit - Perennial forb.

Stems - Ascending to erect, to 1.0 m, unbranched or branched, glabrous or more commonly minutely hairy in 2 narrow, longitudinal bands on opposite sides, the hairs 0.1-0.2 mm long, appearing crinkled.

Ruellia_strepens_stem.jpg Stem and node.

© SRTurner

Leaves - Opposite, simple, petiolate. Petioles 3-20 mm long. Blades of main stem leaves 2-16 cm long, ovate or broadly lanceolate to elliptic or less commonly obovate, mostly tapered to a sharp point at the tip, tapered or less commonly rounded at the base, hairy on both sides and minutely hairy along the margins.

Ruellia_strepens_leaves1.jpg Leaves.

© SRTurner

Ruellia_strepens_leaf1.jpg Leaf adaxial.

© SRTurner

Ruellia_strepens_leaf2.jpg Leaf abaxial.

© SRTurner

Inflorescences - Flower clusters in the axils of main stem leaves and usually also at and near the tip of axillary branches (inflorescence stalks) to 8 cm long, the flowers subtended by hairy lanceolate to obovate leaflike bracts 10-40 mm long.

Ruellia_strepens_inflorescence.jpg Inflorescence.

© SRTurner

Flowers - Calyx lobes 9-20 mm long, 2-4 mm wide, narrowly lanceolate, sparsely to less commonly densely hairy on the back (especially along the midnerve), with a fringe of white hairs 1-2 mm long along the margins. Corollas zygomorphic, 5-lobed, 3-7 cm long, 2-4 cm wide, lavender or bluish. Corolla tube with a whitened, constricted portion at base. Stamens 4, didynamous, adnate at the apex of the constricted portion of the corolla tube. Filaments white, 1.3 cm long, sparsely pubescent at the base, glabrous above. Anthers yellow, 3 mm long. Style to 4 cm long, sparsely pubescent below, white. Stigma 2-lobed, curled. Ovary superior, with some glandular pubescence at apex near style, 4 mm long, 1.3 mm in diameter, conic, 2-locular.

Ruellia_strepens_calyx.jpg Calyx.

© SRTurner

Ruellia_strepens_flower.jpg Flower.

© SRTurner

Ruellia_strepens_flower2.jpg Corolla, calyx, bracts.

© SRTurner

Ruellia_strepens_corolla.jpg Corolla.

© SRTurner

Fruits - Capsules 10-20 mm long, brown, glabrous, explosively dehiscent.

Flowering - May - October.

Habitat - Bottomland and mesic forests, streambanks, pond margins, pastures, moist roadsides, railroads.

Origin - Native to the U.S.

Lookalikes - R. pedunculata.

Other info. - This pretty species is common across most of Missouri. Beyond Missouri its range comprises a patch mostly occupying the U.S. central Midwest, extending in more scattered fashion southward into Gulf Coast states. The plant is easily recognized by its large, petunia-like lavender flowers and deep green, opposite leaves. It is distinguished from Missouri's other two members of the genus by its relatively wide calyx lobes. On the lookalike species, these are very narrow, almost bristlelike. Although the corolla looks regular, it is typically zygomorphic, with one petal being slightly larger than the other four. The flowers of this species only last for one day but the plant produces several flowers while in bloom.

It is common for herbaceous plants to quickly fall down into surrounding vegetation, wilt, and disappear following their bloom period. In contrast, after blooming, R. strepens plants usually remain very much alive, continuing to grow and elongate as the fruits mature. Late season plants are thus typically twice or more the height of flowering specimens, with a characteristic appearance due to noticeable clusters of fruits at the nodes.

Photographs taken at Weldon Spring Conservation Area, St. Charles County, MO, 10-6-2007 and 6-8-2014, and Young Conservation Area, Jefferson County, MO, 7-27-2013 (SRTurner).