Univ. Colorado Stud., Ser. D, Phys. Sci. 2: 189. 1945.
Stems (30-)60-100(-150) cm; base usually reddish, glabrous, glaucous. Leaves mostly cauline; basal leaves absent at anthesis; cauline leaves 3-7 at anthesis; petiole 2-10 cm. Leaf blade round to pentagonal, 1.5-6 × 2-12 cm, nearly glabrous; ultimate lobes 3-12, width 3-24 mm (basal), 1-8 mm (cauline). Inflorescences 15-30(-64)-flowered, cylindric; pedicel spreading, (0.5-)1.5-3.5 cm, glabrous; bracteoles 2-6 mm from flowers, green, linear, 2-5 mm, glabrous. Flowers: sepals rarely reflexed, white to pink, nearly glabrous, lateral sepals spreading, 7-19 × 3-10 mm, spurs straight to upcurved, ascending 30-45° above horizontal, 7-15 mm; lower petal blades elevated, exposing stamens, 3-8 mm, clefts 1-4 mm; hairs centered near base of cleft, ± evenly distributed, white. Fruits 9-18 mm, 2.5-3.2 times longer than wide, puberulent. Seeds: seed coat cells brick-shaped, cell margins undulate, surfaces roughened.
Subspecies 2 (2 in the flora).
Delphinium gypsophilum is sometimes confused with D. hesperium subsp. pallescens, D. recurvatum, and the white-flowered phases of D. hansenii subsp. kernense. The echinate seeds and long-haired petioles of D. hansenii immediately distinguish it from D. gypsophilum, which has neither.
Delphinium gypsophilum is related, and similar in many respects, to D. recurvatum. The two may be distinguished morphologically by their sepals. Delphinium recurvatum has reflexed, blue sepals; those of D. gypsophilum are spreading and white, although they may change to light blue when dry. Plants of D. recurvatum normally are less than 60 cm; those of D. gypsophilum are usually more than 60 cm. Ecologically, D. recurvatum occupies level ground among shrubs, typically in alkaline valley bottoms; D. gypsophilum is found on well-drained hillsides among grasses and in chaparral and oak woodland.
From Delphinium hesperium subsp. pallescens, specimens of D. gypsophilum may be separated by their much more finely dissected leaves, with less surface area, stem base usually reddish, stems frequently glaucous proximally, undulate margins of seed coat cells, and absence of striations in stem base of dried specimens. In contrast, D. hesperium subsp. pallescens has leaves less dissected, with greater surface area, stem base rarely reddish, stem not glaucous proximally, seed coat cells with straight margins, and striations present on the proximal stem of dried specimens.