Penstemon haydenii
Bot. Gaz. 16: 311. 1891. (as Pentstemon haydeni)
Plants: caudex rhizomelike. Stems decumbent to ascending, (15–)20–48 cm, glabrous. Leaves essentially cauline, basal absent or reduced, glabrous; basal and proximal cauline (25–)55–130(–175) × 3–25 mm, blade linear to lanceolate, base tapered, apex acute to acuminate; cauline 2–10 pairs, sessile, 60–110(–120) × 7–30 mm, blade lanceolate to linear, base clasping, apex acuminate to long-acuminate. Thyrses continuous, cylindric, (2–)6–21(–34) cm, axis glabrous, verticillasters (2–)6–10(–17), cymes 1–8-flowered; proximal bracts ovate, 58–120 × 20–45 mm; peduncles and pedicels glabrous. Flowers: calyx lobes lanceolate to linear, 8–13 × 1–3 mm, margins entire or erose, herbaceous or scarious, glabrous; corolla lavender to bluish, usually with magenta nectar guides, ampliate, 21–28 mm, glabrous externally, glabrous internally, tube 7–9 mm, throat abruptly inflated, 9–11 mm diam., rounded abaxially; stamens included, pollen sacs opposite, 1.1–2 mm, sutures papillate; staminode 13–16 mm, included, 1.2–3 mm diam., tip recurved, distal 0.1–5 mm sparsely to densely villous, hairs golden yellow, to 1 mm, rarely glabrous; style 13–23 mm. Capsules 8–12 × 5–9 mm. 2n = 16.
Phenology: Flowering May–Jul(–Sep).
Habitat: Blowouts in sand dunes.
Elevation: 900–2300 m.
Discussion
Penstemon haydenii is known from the Nebraska Sandhills, where extant populations occur in Box Butte, Cherry, Garden, Hooker, Morrill, and Sheridan counties. Historic populations occurred in Thomas County (D. M. Sutherland 1988).
Penstemon haydenii was discovered in northern Carbon County, Wyoming, in the late 1990s some 300 km west of the nearest Nebraska populations; it might have been collected in Wyoming as early as 1877 (W. Fertig 2001). A morphometric analysis of Nebraska and Wyoming plants revealed differences that could justify recognition of Wyoming populations as a distinct variety (C. C. Freeman 2015). It is listed as endangered by the U.S. Department of the Interior.