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. 2 n = 16. Flowering late winter-early summer. Moist talus, cliff faces; 0-2600 m; Calif., Oreg. 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).