Trumpet Penstemon
Penstemon tubaeflorus
Figwort family (Scrophulariaceae)

Description: This perennial plant is 2-3' tall, forming one or more unbranched flowering stalks. The central stem is light green, glabrous, and terete. Pairs of opposite leaves develop along the lower half of this stem; they are up to 5" long and 2" across, deltate-ovate to oblong-lanceolate in shape, and smooth to slightly toothed along their margins. Between the leaves on the lower stem and the inflorescence, the central stem is usually naked; sometimes pairs of small narrow leaves (1" long or less) can be found along the upper stem that resemble bracts. The upper surface of the leaves is medium to dark green and glabrous, while the lower surface is pale green and glabrous.

The inflorescence consists of a cylindrical panicle of flowers about -1' in length. Within this inflorescence, the flowers are clustered together at intervals in pseudo-whorls (about 6-12 flowers per pseudo-whorl). Individual flowers are about -1" long and across, consisting of a funnel-shaped white corolla that flares outward into 5 rounded lobes, a small green calyx with 5 ovate teeth, 5 stamens (one of them sterile), and a pistil with a single style. Tiny glandular hairs occur along the outside and inside of the corolla. The peduncles and pedicels of the flowers are either glabrous or glandular-hairy. The blooming period occurs from late spring to early summer and lasts about 3 weeks. The flowers are replaced by ovoid seed capsules about 1/3" long; the latter eventually split open to release numerous small seeds. The root system consists of a crown with fibrous roots. Low basal leaves are usually present during winter dormancy.

Cultivation: The preference is full or partial sun, mesic to dry conditions, and loamy or rocky soil. Well-drained conditions are required to prevent root rot.

Range & Habitat: Trumpet Penstemon is uncommon in southern Illinois, and rare or absent in the rest of the state (see Distribution Map). Illinois lies near the northeast range-limit of this species. Habitats include meadows and openings in upland woodlands, oak savannas, thinly wooded bluffs, prairies, limestone glades, and prairie remnants along railroads.

Faunal Associations: The nectar and pollen of the flowers attract long-tongued bees primarily: bumblebees, Anthophorine bees (Anthophora spp.), a Mason bee (Osmia distincta), and a wasp (Pseudomasaris occidentalis). The last two insects are oligoleges of Penstemon spp. (Penstemons). Other floral visitors include Green Metallic bees (collect pollen only) Swallowtail butterflies (suck nectar only), and the Ruby-Throated Hummingbird (suck nectar only). Moth caterpillars that feed on Penstemons include Elaphria chalcedonia (Chalcedony Midget), Oncocnemis saudersiana (Saunder's Oncocnemis), and Pyrrhia exprimens (Purple-Lined Sallow). Mammalian herbivores apparently make little use of the foliage as a food source.

Photographic Location: A prairie in Fayette County, Illinois. The photographs were taken by Keith & Patty Horn (Copyright 2010).

Comments: Trumpet Penstemon is an elegant wildflower with an unusually long and slender inflorescence. In addition to these characteristics of its inflorescence, it differs from other Penstemon spp. (Penstemons) by the shape of its flowers (narrow and funnel-shaped at the base, rather than swollen), the large size and similarity of its corolla lobes, the lack of conspicuous leaves between the inflorescence and the leaves of the lower stem, the presence of tiny glandular hairs within its corolla, and the lack of hairs on its leaves and central stalk. Sometimes the scientific name of this species is spelled Penstemon tubiflorus (see Britton & Brown, 1913/1970).