| 1 | Corolla blue to purple; anthers recurved after anthesis |
| 1' | Corolla green, white, cream, or yellow; anthers straight or slightly curved after anthesis |
| 2 | Stem strongly quadrangular, 4-angled to 4-winged along entire length |
| 2' | Stem terete to weakly quadrangular, only 3-4 of most basal internodes may be strongly quadrangular and 4-winged |
| 3 | Upward facing hook present near apex of glandular dorsal area of calyx; bracteole apex acuminate to cuspidate |
| 3' | Glandular dorsal area of calyx lacking an upward facing hook; bracteole apex acute to obtuse |
| 4 | Calyx lobe circular; corolla tubular to salver-shaped; sexual structures positioned within corolla tube; mature fruit orientation erect to horizontal |
| 4' | Calyx lobe ovate; corolla funnel-shaped to campanulate; sexual structures positioned near corolla lobes or slightly exserted; fruit orientation nodding |
| 5 | Plant up to 2.5 m high; stem quadrangular for 3-4 of most basal internodes then abruptly becoming terete, if wings present then 0.1-1.8 mm wide; stigma lobe elliptic; fruit orientation nodding |
| 5' | Plant up to 1.6 m high; stem terete to weakly quadrangular along entire length, if wings or ridges present then 0.1-0.3 mm wide; stigma lobe orbicular; mature fruit orientation horizontal to erect |
| 6 | Leaves elliptic to ovate; calyx 6-14 x 5-10 mm, lobes fused for 1/6-1/5 of total length |
| 6' | Leaves linear, sometimes lanceolate to elliptic; calyx 4-9 x 3-7 mm, lobes fused for ca. 4/5 of total length |
