| | 1. Annual; flowers solitary, axillary |
| P. micranthum |
| | 1' Perennial; flowers clustered generally at stem tips |
| |
| | 2. Leaflets deeply 3–5-lobed (appearing ± whorled); inflorescence head-like |
| |
| | 3. Stamens and style exserted, > corolla tube; petiole base membranous |
| P. chartaceum |
| | 3' Stamens and style included, < corolla tube; petiole base green, not membranous |
| P. eximium |
| | 2' Leaflets entire; inflorescence generally open |
| |
| | 4. Stem erect, < 10 dm; leaves cauline |
| |
| | 5. Corolla generally purple to flesh-pink; fruit 6–8 mm |
| P. carneum |
| | 5' Corolla lobes generally blue; fruit 3–4 mm |
| P. occidentale subsp. occidentale |
| | 4' Stem cespitose, < 3 dm; leaves ± basal |
| |
| | 6. Terminal leaflet ± fused with distal pair; corolla 8–15 mm wide; montane |
| P. californicum |
| | 6' Terminal leaflet generally free from distal pair; corolla 5–8 mm wide; alpine |
| P. pulcherrimum |
| | 7. Corolla white, throat yellow; plant hairy |
| var. pilosum |
| | 7' Corolla blue to purple; plant glandular |
| var. pulcherrimum
|