| | 1. Cauline leaf base wide, clasping; fruit 3–5 cm, round |
| P. somniferum |
| | 1' Cauline leaf base narrow, not clasping; fruit 1–2 cm, narrowly obovate to round |
| |
| | 2. Peduncle hairs appressed; leaf segments linear to lanceolate |
| P. argemone |
| | 2' Peduncle hairs 0 or spreading; leaf segments oblong to lanceolate |
| |
| | 3. Petals 10–20 mm; fruit narrowly obovate; native fire- or disturbance-follower |
| P. californicum |
| | 3' Petals 20–40 mm; fruit widely obovate to round; alien from cultivated |
| P. rhoeas
|