1	"Flowers solitary"	2
1	"Flowers in racemes or cymes"	5
2	"Shrub with rigid, usually spinescent branchlets"	"Hybanthus epacroides"
2	"Perrenial herb or shrub without spinescent branchlets"	3
3	"Plant twining"	"Hybanthus volubilis"
3	"Plant erect, not twining"	4
4	"Anterior petal 4–7 mm long"	"Hybanthus floribundus"
4	"Anterior petal 7–15 mm long"	"Hybanthus vernonii"
5	"Inflorescence usually 10–20 cm long, much exceeding the leafy stems; flowers well-spaced"	6
5	"Inflorescence usually shortly exceeding leaves; flowers close together"	7
6	"Lateral petals lanceolate-falcate; eastern species"	"Hybanthus monopetalus"
6	"Lateral petals oblong; western species"	"Hybanthus calycinus"
7	"Stipules absent"	"Hybanthus debilissimus"
7	"Stipules present"	8
8	"Anterior petal 9–15 mm long"	"Hybanthus cymulosus"
8	"Anterior petal 4–7 mm long"	"Hybanthus floribundus"