| 1 | Plant creeping, rooting at nodes (small herb); leaves petiolate |
| 1' | Plant erect, woody at base; leaves sessile |
| 2 | Flowers sessile; petals reflexed |
| 2' | Flowers pedicellate; petals erect or spreading |
| 3 | Flowers arranged loose, opposite; calyx robust, lobes triangular-ovate; petals narrowly ovate |
| 3' | Flowers arranged congested, verticillate (rarely opposite); calyx not robust, lobes narrowly triangular; petals narrowly elliptic |
| 4 | Mature plants up to 30 cm high; upper leaves longer than inflorescences, keeping these hidden |
| 4' | Mature plants 40-100 cm high; leaves not longer than inflorescences |
| 5 | Flowers with regular distances arranged on up to 30 cm long, mostly terminal racemes; bracts mostly 1-4 mm long, rarely leaf-like at basal flowers; corolla lobes > tube; filaments 3-3.5 mm long, anthers 2.5-3.5 mm long; style 5-6 mm long |
| 5' | Flowers with irregular distances arranged on up to 17 cm long terminal and axillary racemes; bracts 6-55 mm long, leaf-like from base to (almost) apex of raceme; corolla lobes < tube; filaments 2-2.5 mm long, anthers 1.5-2 mm long; style 3 mm long |
