Amsonia jonesii

Stems erect, (15–)23–60(–77) cm, glabrous or sparsely to moderately short-pubescent; branches few, confined to distal part of stem, usually remaining shorter than infructescence, or occasionally absent. Leaves: petiole 1–3(–4.5) mm, glabrous (base pubescent); blades heteromorphic; stem leaf blades ovate, especially proximally, to lanceolate (elliptic, rarely narrowly elliptic), (2–)3.3–5.5(–6.1) cm × (6–)9–25(–32) mm, margins entire, not revolute, not ciliate, apex slightly acuminate (acute), surfaces glabrous; branch leaf blades lanceolate (narrowly elliptic), 2.2–3.9 cm × 3–9(–10) mm. Flowers: sepals narrowly deltate to deltate (subulate, broadly deltate), (0.3–)1–2.5(–4) mm; corolla tube blue, (6–)7.5–8.5(–10) mm, lobes blue, (4–)5–7(–8.5) mm, outer surface of corolla glabrous or bearing villous patches on apical part of tube and basal part of lobes. Follicles erect, (1.4–)3.5–6.5(–9) cm × (2.5–)3–4.3(–4.8) mm, apex short-acuminate to acute, glabrous. Seeds 6–10 × 1.5–2.5 mm.

Phenology: Flowering spring; fruiting summer.
Habitat: Juniper and other woodlands, sagebrush and other arid shrublands, washes, dry prairies and mesas, roadsides, frequently on sand and gravel.
Elevation: 900–2200 m.

Ariz., Colo., N.Mex., Utah.

Discussion

Amsonia jonesii is readily distinguished from other species in its subgenus by its short and relatively broad, often ovate leaves, small blue flowers with usually short sepals (subtended by short, broad bracts), and few, short, or sometimes absent stem branches. Its range extends farther north than that of any other species of subg. Sphinctosiphon. In Arizona, it is confined to Coconino and Mojave counties. A specimen from Utah representing a probable hybrid involving A. jonesii (Thorne & Thorne s.n., ARIZ) has unusually narrow leaves and multiple well-developed branches on each stem.

Selected References

None.

Lower Taxa