Penstemon grandiflorus Nutt.

Large Beardtongue


CC = 8
CW = 5
MOC = 2
SRank = S1

© SRTurner

Family - Plantaginaceae

Habit - Perennial forb.

Stem - Strongly ascending to erect, to 1 m, glabrous, grayish green to grayish brown or grayish purple, strongly glaucous.

Leaves - Basal and opposite, simple. Basal leaves 3-16 cm long, the blade oblanceolate to spatulate or obovate, rounded to bluntly pointed at the tip, mostly tapered basally to a winged petiole, the margins entire, the surfaces glabrous, strongly glaucous. Stem leaves 1.5-11 cm long, the lowermost with the blade oblanceolate to spatulate, grading into circular or depressed-ovate at the stem tip, rounded to bluntly pointed at the tip, the base rounded to shallowly cordate and then clasping the stem, the margins entire, the surfaces glabrous, strongly glaucous.

Penstemon_grandiflorus_leaves.jpg Stem and leaves.

© SRTurner

Inflorescences - Terminal racemes, the central axis glabrous, pale greenish to grayish brown or grayish purple, glaucous, with 3-9 nodes, each with a pair of leaflike, broadly ovate to circular or depressed-ovate, clasping bracts, the relatively short branches ascending, with 2 or 3 flowers per node.

Penstemon_grandiflorus_inflorescences.jpg Inflorescences.

© SRTurner

Penstemon_grandiflorus_inflorescence2.jpg Inflorescence portion.

© SRTurner

Penstemon_grandiflorus_whorl.jpg Inflorescence whorl.

© SRTurner

Flowers - Calyces 7-11 mm long at flowering, glabrous, glaucous, the lobes lanceolate to narrowly ovate. Corollas 35-50 mm long, the tube abruptly enlarged well below the midpoint, strongly bilabiate, the upper lip spreading to somewhat recurved, the lower lip spreading, projecting slightly beyond the upper lip, lavender to pale bluish purple, the throat lined with darker reddish purple nectar guides but not noticeably ridged, glabrous internally and externally. Stamens 4, of two lengths. Staminode white, strongly flattened toward the tip, curled-under and bearded with yellow hairs apically.

Penstemon_grandiflorus_flowers1.jpg Flowers.

© SRTurner

Penstemon_grandiflorus_calyces.jpg Calyces.

© SRTurner

Penstemon_grandiflorus_flowers2.jpg Corollas.

© SRTurner

Fruits - Capsules 16-24 mm long. Seeds 2.5-4.0 mm long, brown to black, the brown to black ridges well-developed.

Flowering - May - June.

Habitat - Loess hill prairies, roadsides.

Origin - Native to the U.S.

Lookalikes - P. cobaea.

Other info. - This beautiful species is rare in Missouri, which lies at the far fringe of the plant's natural range. It is more common in Plains states to our north and west. The species is recognized by its large, lavender flowers and strongly glaucous stems and leaves. The closest lookalike, P. cobaea, has hairy stems which are not glaucous, and usually has deeper purple flowers.

P. grandiflorus is quite showy when in bloom and is an attractive garden candidate, though the bloom period is not long. It has been used at times in highway beautification projects, which may be the origin of the plants pictured above.

Photographs taken along a roadside near Halsey, Thomas County, NE, 6-9-2015 (SRTurner).