Foothill Larkspur

Delphinium hesperium is thought to be poisonous to cattle (D. E. Moerman 1986, no subspecies specified). It is often confused with D . hansenii . See discussion under that species for distinguishing features.

Stems (11-)40-80(-120) cm; base usually reddish, longitudinally ridged, puberulent. Leaves mostly cauline; basal leaves 0-3 at anthesis; cauline leaves 3-8 at anthesis; petiole 0.5-7 cm, petioles of proximal leaves glabrous to puberulent. Leaf blade round to pentagonal, 1-4 × 2-6 cm, usually puberulent, especially abaxially; ultimate lobes 3-14, width 3-8 mm (basal), 2-5 mm (cauline). Inflorescences (5-)15-30(-100)-flowered, moderately open; pedicel (0.5-)1-2.5(-7.5) cm, puberulent; bracteoles 2-6(-12) mm from flowers, green to blue, margins often white, linear-lanceolate, 3-7(-12) mm, puberulent. Flowers: sepals dark blue to white, puberulent, lateral sepals spreading, 7-13(-16) × 3-10 mm, spurs straight to upcurved, ascending 30-45° above horizontal, 9-18 mm; lower petal blades slightly elevated, ± exposing stamens, 3-8 mm, clefts 1-5 mm; hairs centered, denser on inner lobes near base of cleft, white. Fruits 8-18 mm, 2.2-3(-4.2) times longer than wide, sparse puberulent. Seeds not echinate, appearing ± smooth to naked eye; seed coat cells with margins straight, surfaces smooth or roughened.