| | 1. Leaves ephemeral (stem generally leafless), narrowly linear |
| |
| A. albicans |
| A. subulata |
| | 1' Leaves persistent, narrowly linear to broadly ovate |
| |
| | 3. Leaf 1 per node (alternate or clustered) |
| |
| | 4. Leaves alternate to clustered, lanceolate; hoods not elevated above corolla base, subreflexed to spreading at base, ± = anther head |
| A. asperula subsp. asperula |
| | 4' Leaves alternate, linear; hoods elevated above corolla base, ± erect at base, > anther head |
| A. linaria |
| | 3' Leaves > 1 per node (opposite or whorled) |
| |
| | 5. Horn 0 or included in hood |
| |
| | 6. Hoods > or ± = anther head |
| |
| | 7. Corolla purple; leaf sessile, blade base clasping stem |
| A. cordifolia |
| | 7' Corolla greenish yellow; leaf with short petiole, sometimes sessile, blade base rarely clasping stem |
| A. cryptoceras |
| |
| | 8. Stem decumbent to erect; plant densely white-hairy; tops of hoods above base of anther head (hoods, anther head overlapping) |
| A. californica |
| | 8' Stem prostrate; plant ± hairy, purplish or green (appears glabrous at arm's length); tops of hoods below base of anther head (hoods, anther head not overlapping) |
| A. solanoana |
| | 5' Horn exserted from hood (length sometimes < hood) |
| |
| |
| | 10. Corolla red, hoods ± orange; leaves opposite, axillary leaf clusters 0; filament column ± 2 mm; uncommon garden escape |
| A. curassavica |
| | 10' Corolla and hoods greenish to pale yellow; leaves opposite or whorled, often with axillary clusters of small leaves; filament column ± 1 mm; common native |
| A. fascicularis |
| |
| | 11. Hoods > anther head by at least 1/2 their length |
| |
| | 12. Corolla greenish white; hoods generally not elevated above corolla base, ± = exserted horns, ± erect, tips rounded |
| A. nyctaginifolia |
| | 12' Corolla rose-purple; hoods slightly elevated above corolla base, >> exserted horns, ± ascending, tips acute |
| A. speciosa |
| | 11' Hoods not > anther head by at least 1/2 their length |
| |
| | 13. Axillary inflorescences ± sessile |
| A. vestita |
| | 13' Axillary inflorescences peduncled |
| |
| | 14. Leaves opposite, sessile, blade bases often (shallowly) cordate; hoods slightly > anther head |
| A. erosa |
| | 14' Leaves opposite or whorled, sessile to short-petioled, blade bases rarely cordate; hoods slightly < anther head |
| A. eriocarpa
|