1. Mid-stem leaves petioled (petioles winged in N. tabacum); flowers in a paniculate inflorescence.

2. Primary leaves with petioles wingless, not decurrent on the stem; tube of corolla ca. 10-20 mm long.

N. rustica

2. Primary leaves with petioles winged, ± decurrent on the stem; tube of corolla ca. 30-50 mm long

N. tabacum

1. Mid-stem leaves sessile, ± clasping and short-decurrent; flowers in a racemose inflorescence

N. alata