| | 1. Fruit ± black, tip acute; perennial herb; alien |
| P. judaica |
| | 1' Fruit tan to ± brown or reddish brown, tip obtuse; annual; native |
| |
| | 2. Leaf blade ± linear to ovate, base ± tapered, lowest veins generally from midrib; fruit sometimes hidden between calyx lobes |
| P. pensylvanica |
| | 2' Leaf blade round to ovate, base generally truncate to cordate, lowest veins often from basal margin; fruit hidden between calyx lobes |
| P. hespera |
| | 3. Leaf blade ± round, width = length; calyx lobes spreading to recurved, acuminate |
| var. californica |
| | 3' Leaf blade ovate, wider than long; calyx lobes erect, acute |
| var. hespera
|