Penstemon digitalis Nutt.

Smooth Beard-Tongue

Penstemon digitalis plant

Family - Scrophulariaceae

Stems - To +1m tall, glabrous below (sometimes with minute hairs in vertical lines), glandular pubescent above, simple to somewhat branching, herbaceous, from a thick caudex.

Penstemon digitalis stem

Leaves - Opposite or rarely in whorls of 3s, petiolate below to sessile above, glabrous, with punctate dots below, entire or shallow serrate.. Petioles to 8cm long. Blades variously shaped from spatulate to lanceolate, to 20cm long, +5cm broad, reduced at inflorescence.

Penstemon digitalis leaves

Inflorescence - Terminal thryse to 20 cm tall(long). Cymes in +/-5 verticillasters. Cymes with typically +/-3 flowers each. Peduncles and pedicels spreading away from stem or sub-erect, dense glandular pubescent (the glands often blackish). Each division of inflorescence subtended by pair of attenuate bracts (reduced upward).

Flowers - Corolla bilabiate, white, 2.5-3cm long, glandular and non-glandular pubescent externally, glabrous internally. Corolla tube constricted in basal half, less constricted in apical half. Upper lip of corolla 2-lobed. Lower lip 3-lobed. Lobes rounded to obtuse, 3-5mm long and broad. Stamens 4, adnate near apex of constricted portion of corolla tube. Staminode 1. Filaments to 2cm long, white, glabrous. Anthers purplish-black, 3mm long. Style 2cm long, white, glabrous. Ovary green, glabrous, 4mm long. Calyx 5-lobed. Lobes ovate to lance-ovate, acute to acuminate, glandular pubescent, 4-5mm long, 3mm broad. Capsule to 1.5cm long.

Penstemon digitalis calyxCalyx close-up.

Penstemon digitalis corollaCorolla.

Penstemon digitalis corollaCorolla again.

Flowering - May - July.

Habitat - Rich woods, prairies, thickets, roadsides, railroads. Also cultivated.

Origin - Native to U.S.

Other info. - This is the most common species of the genus in Missouri, being found in almost every county except in the extreme northwest corner of the state.
Steyermark lists two varieties for this species in Missouri. Form digitalis, pictured above, has leaves which are opposite. Form baueri, has leaves in whorls of 3s. This latter form is rare.
The flowers resemble those of the genus Digitalis, hence the species name.
Many species of the genus Penstemon look alike at first glance. Check them out carefully to be sure which one you really have.

Photographs taken off Hwy V, Shannon County, MO., 5-23-03.