16. Delphinium geyeri Greene, Erythea. 2: 189. 1894.
Geyer's larkspur, poisonweed
Stems (15-)30-60(-80) cm; base usually reddish, puberulent. Leaves distribution variable; basal leaves 0-4 at anthesis; cauline leaves 4-22 at anthesis; petiole 0.4-10 cm. Leaf blade light green, ± round, 1-5 × 1-6 cm, densely pubescent; ultimate lobes 7-20, width 2-5 mm (basal), 2-4 mm (cauline), apex gradually tapering to point; veins obscure. Inflorescences 6-30(-60)-flowered, ± open, cylindric; pedicel ascending to spreading, 1-3(-4) cm, puberulent; bracteoles 1-3 mm from flowers, green, lanceolate, 3-6 mm, puberulent. Flowers: sepals bright blue, puberulent, lateral sepals spreading, 10-18 × 4-8 mm, spurs straight to slightly downcurved, ascending 0-30° 11-16 mm; lower petal blades slightly elevated, ± exposing stamens, 4-8 mm, clefts 0.5-2 mm; hairs centered, densest on inner lobes near base of cleft, white to light yellow. Fruits 11-15 mm, 3-3.5 times longer than wide, sparse puberulent. Seeds unwinged; seed coat cells with margins straight, surfaces ± roughened. 2 n = 16.
Flowering late spring-early summer. Grasslands or Artemisia-Cercocarpus scrub; 1400-3000 m; Colo., Mont., Nebr., Utah, Wyo.
Apparently closely related to Delphinium stachydeum , D . geyeri is generally smaller, earlier flowering, with more finely dissected leaves and a more eastern geographic distribution.