Ruellia strepens L. - Wild Petunia

Ruellia strepens plant

Family - Acanthaceae

Stems - To 1m tall, erect, simple or branching, herbaceous, somewhat angled, glabrous or with pubescence in vertical rows.

Ruellia strepens stem

Leaves - Opposite, petiolate, ovate, ovate-lanceolate, to oblong, typically entire or merely crenulate, glabrous to sparsely hairy, to 15cm long, 6cm wide. Petiole typically winged.

Inflorescence - One or two flowers, on peduncle, from leaf axils near middle of stem. Flowers subtended by a pair of foliaceous bracts.

Flowers - Corolla zygomorphic, to +5cm long, +/-4cm broad, 5-lobed, typically blue. Corolla tube with a constricted portion at base. Constriction white, to 2.5cm long, 3mm in diameter. Expanded portion of corolla tube to +1cm long, 1cm in diameter, pubescent. Corolla lobes +/-1.5cm long and broad, glabrous internally, pubescent externally with some glandular pubescence near the base. Stamens 4, didynamous, adnate at the apex of the constricted portion of the corolla tube. Filaments white, 1.3cm long, sparse pubescent at the base, glabrous above. Anthers yellow, 3mm long. Style -4cm long, sparse pubescent below, white. Stigma 2-lobed, curled. Ovary superior, with some glandular pubescence at apex near style, 4mm long, 1.3mm in diameter, conic, 2-locular. Calyx tube to 5mm long, 5-lobed. Lobes linear-lanceolate, 2-3cm long, 3mm broad, with long and short glandular pubescence, entire, erect. Capsules brown, glabrous, to 2cm long, explosively dehiscing.

Ruellia strepens calyxCalyx.

Ruellia strepens flowerCorolla.

Flowering - May - October.

Habitat - Waste ground, disturbed sites, moist, open woods, streambanks.

Origin - Native to U.S.

Other info. - 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 many flowers while in bloom. This species is common and reminds many people of the non-related "Petunia" of cultivation.
Steyermark lists three forms for the plant based on flower color and size. Form strepens is shown above. Form alba Steyermark has a white corolla. Form cleistantha (Gray) McCoy has cleistogamous flowers but may not be a distinct form, rather a phase of form strepens.

Photograph taken at the Kansas City Zoo, 5-28-99, and in the Ozark Scenic Riverways, 6-3-03.


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