Plants of the Eloise Butler Wildflower Garden
The oldest public wildflower garden in the United States






Foxglove Beardtongue
Penstemon digitalis Nutt. ex Sims formerly P. laevigatus

Figwort (Scrophulariaceae)

new family - Plantaginaceae
Late Spring to Early Summer
Other names and notes

(Talus Slope Penstemon, White Beardtongue, Tall Beardtongue, False Foxglove). Beardtongues have 3/4 to 2 inch long trumpet shaped 5-parted flowers with flaring lobes, five stamens and specifically the flower throat is open with a flat base. The stem will have opposite, stalkless leaves. The Foxglove or White Beardtongue is a perennial whose stems are erect, smooth and purplish color with a height of one to four feet. Leaves are lance shape, broad at the base where they touch the stem (no stalks); they have a shiny appearance and have fine teeth on the edges. The central leaf vein is prominent. The plant has a basal rosette of leaves that are stalked - these remain after the stem leaves have dropped off and the seeds have matured. The inflorescence is a panicle of stalked flowers atop the stem. The flowers have a white corolla sometimes with purple veining for nectar guides. The upper lip has two rounded lobes and the lower lip has three. The flower tube is longer than the flaring lobes but short enough to let the stamens be accessible within the lobes. There are 4 true stamens and a single style which hug the upper part of the corolla tube. A fifth staminode (infertile or false stamen) lies at the bottom of the tube and protrudes with a hairy tip. The base of the trumpet tube is flat. The green calyx has 5 long-pointed lobes that are reflexing. The outer surface of the corolla and the calyx have hair, the only parts of the plant with hair. Seed: Flowers mature to brown clusters of ovoid seed capsules which then split open to release numerous dry brown flattened angled seeds. These are shaken out of the capsule by the wind.

Habitat: The plant grows best in full sun, but will tolerate some shade (if you don't mind stems leaning toward the sun) with adequate moisture in loamy type prairie soils. It grows from a fibrous root system and forms a woody caudex. It will self-seed. Names: Penstemon is from the Greek pente, or "five," and stemon, refers to "stamen." Digitalis refers to the finger shape of the flower. Contemporary Botanists have now placed the Penstemons into the family Plantaginaceae. The name 'Beardtongue' refers to the hairy tip of the sterile stamen that is visible in the corolla. The author names for the plant classification, 'Nutt. ex Sims' refer to Thomas Nuttall (1786-1859) English botanist who lived and worked in America from 1808 to 1841. On his many expeditions he collected many species that had been originally collected by Louis and Clark but lost by them. His work was incomplete and updated and republished by John Sims (1749-1831), English botanist, first editor of Curtis’s Botanical Magazine, founding member of the Linnean Society, plant collector and author. In earlier years this species was classified as P. laevigatus. Comparison: Another Beardtongue which has pinkish to lavender blue flowers is the Showy Beardtongue, Penstemon grandiflorus Nutt., but there the flowers are clustered in 2s or 4s along the upper stem leaf axils; and Pale Beardtongue where the stems and flowers are hairy, and the flowers are white and smaller with the entire plant much shorter.

Foxglove Beardtongue
foxglove Beardtongue flower panicle
Foxglove Beardtongue
Foxglove Beardtongue
Above: Note the delicate veins of the nectar guides in the flower tube and the fine hair on the outside and on the tip of the sterile stamen - the only parts of the plant with hair.

Foxglove Beardtongue

Seed Capsules
Below: The stem leaves are sessile (no stalks), shiny green and have small teeth on the edge. Above and below: The seed capsules of the Beardtongues are ovoid in shape and contain numerous flattened angled seeds.
Foxglove Beardtongue leaf seeds
Basal rosette Foxglove Beardtongue root
Above: The rosette of basal leaves, which are stalked and remain as the plant forms seeds and the stem leaves have dropped away. Above: The fibrous root system of Foxglove Beardtongue.

Below: An extensive grouping on the Goldenrod Trail at the far east end of the Upland Garden.

Foxglove Beardtongue Group

Notes: Eloise Butler introduced this species to the Garden on April 30, 1915 with 6 plants sourced from Horsford's Nursery in Charlotte Vt. Then on June 21 and June 29, same year, she sourced more from right within Glenwood Park (which surrounded part of the Garden. Martha Crone noted planting this species several times, totaling 80 plants, in the fall of 1937. Like Eloise, she used the prior scientific name of P. laevigatus Ait. var. digitalis. She did not list her source for the plants. However, by the time of her 1951 inventory of plants in the Garden, she did not list it, but she did list four other Penstemons, (two of which are considered native in Minnesota): Large-flowered Beardtongue (P. grandiflorus) (native), Slender Beardtongue, (P. gracilis) (native), Western White Penstemon (P. confertus), and Blue Western Penstemon (P. caelestinus). The plant was again listed on the 1986 Garden Census.

Native or introduced? P. digitalis has been found in five counties of Minnesota but the DNR listing states it is not determined if the plant is native to the state or introduced from another area. The U of M Herbarium authorities do not note it as introduced, thus leaning toward native or long-since naturalized.

The four Penstemons definitely considered native to Minnesota are: P. grandiflorus, Large-flowered Beardtongue; P. albidus, White Penstemon; P. gracilis, Lilac Penstemon; P. pallidus, Pale Beardtongue.


References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applies. Distribution principally from Wi, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.  
©2013 Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "" 092114