Delphinium bicolor subsp. calcicola
in M. J. Warnock, Phytologia 78: 90. 1995.
Flowers: sepals bright dark blue, lateral sepals 16-21 × 9-12 mm, spurs 15-23 mm; lower petal blades with cleft 2 mm or more; hairs usually yellow.
Phenology: Flowering late spring–early summer.
Habitat: Rocky soils in shortgrass prairie and sagebrush communities on limestone outcrops
Elevation: 1300-2100 m
In the field, Delphinium bicolor subsp. calcicola is readily separated from D. bicolor subsp. bicolor on the basis of its brighter colored, slightly larger flowers and its edaphic preference. Delphinium bicolor subsp. calcicola usually flowers somewhat later where the two are sympatric. These differences are often not apparent from herbarium specimens. Specimens of this taxon misidentified as D. geyeri account for most reports of that species from Montana.