Lablab purpureus
The Hyacinth bean is a perennial vine up to 5 or 6 m high that climbs by twining and scrambling.
Stems are herbaceous but older ones, and the base may be slightly woody.
The much-branched stems are often purple.
Young stems may have some hairs that are stiff and lie along the surface.
The alternate trifoliate leaves are on a green or purple petiole.
There is a green swelling or pulvinus at the base of the petiole that allows for movement of the leaf.
There is a pair of stipules on the stem beside the base of the petioles.
Stipules are around 5 mm long they are ovate to lance-shaped.
The midrib holding the leaflets is around 3 cm long.
Leaflets are on a petiolule around 3 to 4 mm long.
Leaflets are variable in shape and size but all have a pointed tip and a flat or wedge-shaped base.
They are wide to narrowly ovate, triangular or diamond-shaped and around 3 to 12 cm long and wide.
The lateral pair have unequal sides.
The petiole and petiolules may have short hairs.
There are small hairs on the lower surface and very small ones on the edges.
Inflorescences are vertical spikes with a peduncle around 20 (40) cm long.
They are axillary with small leaf-like bracts at the base of the peduncles.
The hairy ovate to lance-shaped bracts, up to 4 mm long are deciduous.
The midrib holds up to around 15 flowers with around 3 at each swollen node.
The lower flowers open first.
Flowers are on a 3 mm long pedicel with 2 bracteoles and both may have hairs.
Flowers are typical pea-like ones with a large erect standard, 2 vertical wings and 2 keel petals.
The 6 to 7 mm long calyx has a basal tube 3 to 4 mm long with 2 lips.
The upper lip has a rounded tip that may have a notch and the lower lip has 3 unequal lobes.
There may be hairs on the outer surface.
The erect obovate to almost round standard is around 14 mm across.
Just above its narrow claw base are 2 raised narrow linear appendages or calli.
The 2 wing petals enclose the keel petals.
The 2 keel petals are fused along their lower edges.
The 15 mm long sickle-shaped keel petals enclose the stamens and style.
The standard and wings are mauve to purple but fade to white, the keels are white.
The flattened superior ovary has 1 locule with several ovules.
The stout apical style, slightly curved outside the stamen tube has some hairs on one side.
The oblong flattened pods are around 7 cm long and 1.5 cm wide.
The retained style makes a beak at the tip.
The upper suture has tiny nodules.
Pods have up to 5 blackish-purple seeds that have a linear white aril at the point of attachment to the placenta.
Pods have tiny hairs on a nodular base and may have longer simple hairs.
There 4 subspecies or forms.
J.F.
