Flora of North America species comparison

Hybrids between Delphinium cardinale and D. parryi have been named D. ×inflexum Davidson. Because of horticultural interest in red-flowered delphiniums, garden hybrids have been made with D. elatum, D. hesperium, D. hutchinsoniae, D. nudicaule, D. parishii, D. penardii, D. scopulorum, D. tatsienense Franchet, D. uliginosum, and D. zalil Aitchison & Hemsley, although D. cardinale does not grow with any of these in the wild.

Plants of Delphinium cardinale are quite variable in size, leaf distribution, and pubescence, resulting in considerable differences between, and sometimes within, populations. No patterns could be seen, however, to justify recognition of separate taxa within D. cardinale. Populations farther south (in Baja California, Mexico) may represent a distinct entity; they require further study.

The only possible confusion between Delphinium cardinale (seeds not ringed, fruits erect, grows in relatively dry sites) and another taxon might occur with Delphinium nudicaule (seeds ringed, fruits spreading, grows in moist habitats). The two are separated geographically and phenologically (although D. cardinale may begin flowering in southern California before D. nudicaule has finished in northern California).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Subspecies 2 (2 in the flora).

Delphinium nuttallii has often been confused with D. menziesii; it may be distinguished by consistently smaller flowers and usually more flowers per plant than in the latter. Interestingly, each species produces both blue-purple and yellowish flower colors, in separate populations.

(Discussion copyrighted by Flora of North America; reprinted with permission.)