Global description
Crotalaria senegalensis is an erect plant, subwoody at the base and covered with a short pubescence. It has alternate, trifoliate leaves with petioles as long as the leaflets. These are obovally shaped. The base of the petiole is framed by two very small linear stipules. The flowers are arranged in loose terminal and lateral racemes located opposite to the leaves. They are yellow and red. The fruit is a short pubescent inflated pod, terminated by a short beak. It contains smooth, shiny seeds of brown color.
Cotyledons
The cotyledons are reniform.
First leaves
The first leaves are alternate and compound, trifoliate. They are borne by a petiole as long as the leaflets. These are obovate to elliptical in shape. The summit is rounded and mucronate. The upper side of the blade is marked with 5 to 7 pairs of slightly arched veins. The base of the petiole is framed by two very small linear stipules.
General habit
Crotalaria senegalensis has an erect habit or can be found spreading on the ground. The plant is bushy, subligneuse at the base and can measure 30 to 60 cm in height.
Underground system
The root is a taproot.
Stem
The stem is cylindrical and solid. It is covered with a short pubescence.
Leaf
The leaves are alternate and compound, trifoliate. They are borne by a petiole as long as the leaflets (2 to 3 cm). At the base of the petiole are two very small linear stipules. The leaflets are subsessile. The limb is obovate in shape. It is 15 to 30 mm long and 7 to 15 mm wide. The base is in acute corner and the summit is rounded and provided with a short mucron. The terminal leaflet is slightly more developed than the lateral leaflets. The margin is entire. The upper surface is glabrous whereas the lower surface is covered with a weak, short pubescence. The limb is traversed by 5 to 7 pairs of slightly arched secondary veins.
Inflorescence
The flowers are arranged in loose terminal racemes and in lateral racemes located opposite to a leaf.
Flower
The flowers are borne by a short pedicel of 1 to 2 mm. The calyx is welded at the base and divided into 5 triangular teeth longer than the tube. It is 3 to 5 mm long and finely pubescent. The corolla is composed of a rounded upper petal (standard) of yellow color and strongly streaked with red on the upper face, 2 lateral petals (wings) and a lower petal (hull) containing the stamens, yellow. The hull is sharply curved near the base. The corolla is 7-12 mm long. The threads of the stamens are all welded at the base into a tube.
Fruit
The fruits are inflated pods, 13 mm long and 6 to 8 mm wide. The apex ends with a short beak corresponding to the base of the style. In young fruits, this beak is prolonged by style, forming a pronounced angle. The tegument is finely pubescent. The pod contains 6-8 seeds.
Seed
The seeds are flattened ellipsoidal in shape with a curved lateral appendage. They are 2 mm long and 1.5 mm wide. The integument is smooth and shiny, brown in color.