Global description
Leonotis nepetifolia is a large herbaceous plant reaching 2m high, with a square stem with concave sides. Emitting a strong odor. The leaves are simple, opposite, stalked with oval serrated lamina. The inflorescences are large clusters in the axils of leaves, forming prickly balls, 4 to 6 cm in diameter (corresponding to the assembly of tubular calyx with spiny tines). From these glomeruli, are tubular corolla of bright orange, sometimes cream, 15 to 20 mm long, ending with an upper lip two times longer than the lower lip. The fruit is an achene, 3 to 3.5 mm.
Cotyledons
The cotyledons are petiolate, with a rectangular to oblong lamina, 2 cm long and 1 cm wide.
First leaves
The first leaves are opposite, decussate, simple, stalked, with ovate lamina and serrated margin.
General habit
Robust herbaceous plant, erect, reaching up to 2 m high.
Underground system
Tap root
Stem
The stem is solid, of quadrangular section with scabrous edges and concave sides. It can reach 15 mm in diameter.
Leaf
The leaves are simple, opposite, decussate. They are carried by a petiole, 5 to 10 cm. The lamina is oval with truncate or sub-cordate base, acute apex and serrated to crenated margin. It measures 7 to 11 cm long and 3 to 6 cm wide. Both sides are puberulous. The terminal leaves are smaller and more or less elliptical with a wedged base.
Inflorescence
Inflorescences are formed of large axillary glomerules, 4 to 6 cm in diameter, surrounding the stem. At the base are spinous bracts, 10 mm long.
Flower
The tabulate calyx are of 11 to 20 mm long, pubescent wall, and are surmounted by two spiny tine. The tow upper tines are 4 to 5 mm long and the three lower tines1.5 to 2 mm long. The corolla consists of a tube 15 to 20 mm long, villous of dark orange to cream. The tube is surmounted by a long upper lip of 5 to 7 mm, two times longer than the lower lip.
Fruit
The fruit is an achene, 3 to 3.5 mm, which remains included in the tube of calyx.