Snowfield sagebrush

Artemisia tridentata Nuttall subsp. spiciformis (Osterhout) Kartesz & Gandhi; Seriphidium spiciforme (Osterhout) Y. R. Ling

Shrubs, 30–80 cm (widely branched, gray-tomentose), aromatic; root-sprouting. Stems relatively numerous, brown or grayish green. Leaves ± deciduous (by late summer, turning yellow); blades lanceolate, oblanceolate, or cuneate, 2.5–5.5 × 0.8–1.2+ cm, entire or irregularly 3–6-lobed (lobes to ¹/3 blade lengths, 1.5+ mm wide, rounded or acute; leaves of flowering stems usually smaller, entire), faces ± sericeous or tomentose. Heads (erect) in (leafy) paniculiform arrays 8–15(–25) × 0.5–3(–4) cm. Involucres ovoid or lanceoloid, (2.5–)4–6(–7) mm. Phyllaries lanceolate, sparsely to densely hairy. Florets 8–18(–27); corollas 2.5–3.5, glabrous. Cypselae 1–1.5 mm, glabrous or resinous. 2. = 18, 36, 54, 72.

Flowering mid summer–fall. Moist open slopes, rocky meadows, streamsides, woodlands, late-lying snowfields; 2100–3700 m; Calif., Colo., Idaho, Nev., Oreg., Utah, Wash., Wyo.

Often confused with Artemisia rothrockii, A. spiciformis has been recognized only recently as a widespread, high-elevation sagebrush of late-lying snowfields. Molecular analysis has not yet determined the degree to which this species intergrades with A. cana subsp. viscidula and A. tridentata subsp. vaseyana, the presumed parents of this putative hybrid. Because snow-field sagebrush produces fertile seeds and forms a stable community type, it is treated here as a distinct species.