Stems 100-200(-250) cm; base sometimes reddish, glabrous, glaucous. Leaves cauline, 12-22, absent from proximal 1/5 of stem at anthesis; petiole 5-13 cm. Leaf blade round to pentagonal, 7-12 × 10-20 cm, nearly glabrous; ultimate lobes 5-15, width 6-30 mm, tips gradually tapered to mucronate apex; midcauline leaf lobes more than 3 times longer than wide. Inflorescences 40-90(-180)-flowered; pedicel 0.5-2 cm, puberulent; bracteoles 4-6 mm from flowers, green to purple, linear, 5-8 mm, puberulent. Flowers: sepals bluish purple to pale lavender, nearly glabrous, lateral sepals ± forward pointing, 9-14 × 4-6 mm, spurs slightly decurved, 30-45° above horizontal, dark blue, 10-13 mm; lower petal blades ± covering stamens, 5-7 mm, clefts 2-3 mm; hairs centered, mostly on inner lobes near base of cleft, yellow to white. Fruits 13-18 mm, 3-4 times longer than wide, puberulent. Seeds wing-margined; seed coat cells elongate, surfaces smooth.
Flowering summer. Riparian woodlands, subalpine meadows; of conservation concern; 2200-3000 m; Colo., N.Mex.
Delphinium robustum is the representative of the southern Cordilleran complex from the Jemez, San Antonio, San Juan, San Pedro, and Sangre de Cristo mountains. Hybrids are known with D . sapellonis .