Fl. N. Amer. 1: 33. 1838
Stems (15-)20-50(-125) cm; base reddish, glabrous. Leaves mostly on proximal 1/3 of stem; basal leaves 2-7 at anthesis; cauline leaves 3-4 at anthesis; petiole 0.5-14 cm. Leaf blade round to pentagonal, 2-6 × 3-10 cm; ultimate lobes 3-12, width 5-40 mm (basal), 2-20 mm (cauline). Inflorescences 5-20(-69)-flowered; pedicel (1.5-)2-6(-8) cm, glabrous to glandular-pubescent; bracteoles 14-20(-30) mm from flowers, green to red, linear, 2-4(-9) mm, glabrous to puberulent. Flowers: sepals scarlet to reddish orange, rarely dull yellow, glabrous, lateral sepals forward-pointing to form pseudotube, (6-)8-13(-16) × 3-6 mm, spurs straight, slightly ascending, (12-)18-27(-34) mm; lower petal blades elevated, exposing stamens, 2-3 mm, clefts 0.5-1 mm; hairs sparse, evenly dispersed, yellow. Fruits 13-26 mm, 3.5-4.5 times longer than wide, glabrous. Seeds unwinged or sometimes slightly wing-margined; seed coat cells with surfaces smooth. 2n = 16.
Phenology: Flowering late winter–early summer.
Habitat: Moist talus, cliff faces
Elevation: 0-2600 m
Delphinium nudicaule hybridizes with most other taxa of Delphinium that it encounters. Apparent hybrids involving D. nudicaule, and seen by the author (either afield or as specimens), include D. andersonii, D. antoninum, D. decorum, D. luteum, D. nuttallianum, D. patens, and D. trolliifolium. In addition, garden-grown plants have been hybridized with D. cardinale, D. elatum, D. menziesii, D. parishii, D. penardii, D. tatsienense Franchet, D. triste Fischer ex de Candolle, and D. uliginosum; D. nudicaule does not naturally occur with these species. Delphinium nudicaule is one of the earliest larkspurs to flower in any given locality. Douglas's type collection of D. nudicaule represents plants (synonyms D. sarcophyllum Hooker & Arnott and D. peltatum Hooker, an invalid name) grown under very moist conditions, probably quite near the ocean. The type specimen of D. armeniacum A. Heller represents plants grown under unusually dry conditions.
The Mendocino Indians consider Delphinium nudicaule a narcotic (D. E. Moerman 1986).