| 1 | Corolla red |
| 1' | Corolla yellow, lavender, or white |
| 2 | Corolla tube 3-3.5 cm long, nearly straight, roseate in the throat, 5 lobes spreading |
| 2' | Corolla tube ≤ 2.5 cm long, curved at middle, yellow in the throat, 2 dorsal lobes recurved (cultivated) |
| 3 | Corolla yellow; calyx lobes obovate |
| 3' | Corolla white or lavender; calyx lobes lanceolate or spathulate |
| 4 | Leaf blade pale green; corolla white; calyx lobes lanceolate |
| 4' | Leaf blade dark with pale markings along the main veins; corolla tube white with lavender lobes; calyx lobes spathulate (cultivated) |
