Penstemon cobaea Nutt. - Purple Penstemon

Penstemon cobea plant

Family - Scrophulariaceae

Stems - Single or multiple from the base, erect, herbaceous, to +70cm tall, terete, densely puberulent below, densely glandular puberulent above, mostly simple but branching in the inflorescence, light green.

Penstemon cobea stem

Leaves - Opposite, sessile, many on the stem, the lower leaves spatulate, upper leaves ovate, serrate, shiny dark green above, dull shiny green below, sparse puberulent above, more so below. Leaves abruptly reduced in the inflorescence (bracts). Lowest leaves to 15cm long, 3cm broad. Upper leaves 5-6cm broad and shorter.

Penstemon cobea leaves

Inflorescence - Axillary cymes in the upper leaf axils. Each division of the cymes subtended by a reduced ovate-lanceolate bract. Bracts densely glandular pubescent. Peduncles densely glandular pubescent. Pedicels glandular pubescent, 3-5mm long.

Flowers - Corolla purple, glandular pubescent externally, abruptly contracted at the base for about 1.5cm. Corolla tube +/-4cm long, 5-lobed at the apex. Lobes rounded, 2 upper and 3 lower, to 1.5cm long and broad. Corolla with darker purple stripes internally and some white at the throat on the lower 3 lobes. Stamens 4, didynamous, adnate at the base of the corolla tube, curved, resting against the upper portion of the corolla tube, included. Filaments white, +3.5cm long, glabrous. Anthers purplish (pale), 2-lobed, +4mm long, 3mm broad. Staminode 1, exserted past the stamens to the throat of the corolla tube, white, adnate at the apex of the apex of the contracted portion of the corolla tube on the dorsal portion, 3cm long, with long sub-retrorse hairs. Hairs of the staminode brown near the base of the staminode and white near its apex, glandular, 2-4mm long. Pistil 1, white, glabrous, +3cm long, thin, resting against the upper portion of the corolla tube and curved downward. Ovary green, glabrous, ovoid, +/-4mm long, +2mm in diameter. Calyx green, densely glandular puberulent, 5-lobed, the tube 2mm long. Lobes 1.1cm long, 5mm broad, acute, glabrous internally, oblong, green. Calyx lobes slightly overlapping.

Penstemon cobea corollaCorolla.

Penstemon cobea corollaSide view.

Penstemon cobea calyxCalyx.

Flowering - April - June.

Habitat - Limestone glades, bald knobs, limestone mounds, cultivated.

Origin - Native to U.S.

Other info. - This striking species can be found growing wild in just a small handful of south-central Missouri counties. The plant is, however, widely cultivated and can be found throughout the state in gardens and landscapes. The big purple flowers are hard to miss. This species does well in a garden setting but apparently does not like much competition.

Photographs taken in Columbia, MO., 5-18-04.


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