Ind. Sem. Hort. Petrop. 3: 650. 1837.
Stems 5-25 (-42) cm; base reddish or not, at least two proximal internodes long-pubescent. Leaves mostly on proximal 1/3 of stem; basal leaves 1-6 at anthesis; cauline leaves 2-4 at anthesis; petiole 0.5-7 cm. Leaf-blade deltate to pentagonal, 1-2.5 × 1.5-4.5 cm, ± puberulent; ultimate lobes 3-15, width 3-17 mm (basal), 1-8 mm (cauline), widest at middle or in proximal 1/2. Inflorescences 2-10 (-20) -flowered; pedicel 1-4 (-6) cm, puberulent to glabrous; bracteoles (3-) 7-11 (-21) mm from flowers, green to blue, linear-lanceolate, 6-9 (-12) mm, puberulent. Flowers: sepals bluish purple (somewhat faded on drying), puberulent, lateral sepals spreading, (11-) 15-20 (-24) × 6-11 (-15) mm, spur straight, 0-30° above horizontal, 13-20 mm; lower petal blades ± covering stamens, 6-11 mm, cleft 2-4 mm; hairs on entire surface, densest on inner lobes, yellow or white. Fruits 9-20 mm, 3-4.5 times longer than wide, glabrous to puberulent. Seeds wing-margined; seed-coat cells ± aggregate in small wavy ridges, cell surfaces ± roughened, without swollen, blunt hairs.
Subspecies 2 (2 in the flora).
Delphinium decorum and D. menziesii have been confused. Delphinium menziesii usually has darker, colorfast (nonfading) sepals with less lavender, and a more northern distribution than D. decorum. It also has more finely dissected leaves than D. decorum subsp. decorum.
Often confused with Delphinium patens, D. decorum is sometimes circumscribed to include that species. The spreading, fading, blue-purple sepals, pubescent proximal portion of stems, and large lower petal blade of D. decorum, compared to the reflexed, colorfast, bluer sepals, proximally glabrous stems, and smaller lower petal blades of D. patens, adequately distinguish the two taxa.
No values specified.