Key to Onosma serpentinica and O. argentata

1. Leaves 70–90× 3–5.5 mm, adpressed setose; 17–25 flowered cymes; corolla white to cream, hairy; filament 4 mm; style 18–22 mm, nutlets 4× 3 mm ................................................................................................................................................................ O. argentata

1. Leaves 10–50× 2–10 mm, patent setos; 4–7 flowered cymes; corolla white to cream–white at first, becoming pink or purple and finally bluish-violet or intense purple, papillate to scabrid-papillate; filament 6–7 mm; style 25–28 mm, nutlets 4.5–5.5× 3–3.5 mm ............................................................................................................................................................................... O. serpentinica