Rocky Mountain larkspur

Delphinium macrophyllum Wooton

Stems 50-120 cm; base often reddish, puberulent, midstems glabrous to subglabrous. Leaves mostly on proximal 1/3 of stem; basal leaves (0-)3-7 at anthesis; cauline leaves 6-15 at anthesis; petiole 0.5-15 cm. Leaf blade round to pentagonal, 1.5-10 × 2-16 cm, nearly glabrous; ultimate lobes 5-19, width 5-30 mm (basal), 1-10 mm (cauline). Inflorescences 10-30-flowered, open, cylindric; pedicel ascending to spreading, 1-3(-4.5) cm, puberulent; bracteoles 2-7 mm from flowers, green, linear, 2-4 mm, puberulent. Flowers: sepals bright dark blue, nearly glabrous, lateral sepals forward pointing, 12-15 × 4-6 mm, spurs gently decurved, slightly ascending, 15-20 mm; lower petal blades ± covering stamens, 5-8 mm, clefts 1-3 mm; hairs sparse, centered, mostly below junction of blade and claw, white. Fruits 16-20 mm, 4-4.5 times longer than wide, nearly glabrous. Seeds wing-margined; seed coat cells with margins straight, cell surfaces ± roughened. 2 n = 16.

Flowering late summer-early autumn. Riparian forests and open woodlands; 1700-2600 m; Ariz., N.Mex; Mexico (Sonora).

Hybrids are known with Delphinium andesicola .