Global description
Ocimum gratissimum is a perennial herbaceous, aromatic plant, with erect and branched stem, 0.40 to 2 meters high. The stem is rounded-quadrangular, highly branched, woody, rigid and with epidermis peeling off in strips at the base, more or less glabrous but becoming pubescent at nodes and on the inflorescences axis. The leaves are very fragrant are simple, petiolate, opposite, elliptic or oval to broadly ovate, with serrated margins. Small white flowers sometimes pink or carmine red, with a small calyx, are arranged in a terminal inflorescence in fake spike of 7 to 20 cm long. The fruits are formed of spherical capsules of about 2 mm in diameter.
Growth Habit
Ocimum gratissimum is a sub-woody, erect, abundantly branched herbaceous plant. It measures 1 to 2 meters (up to 3 m) high. It has a strong aromatic smell.
Underground system
Taproot.
Stem
The stem is rounded- quadrangular, highly branched, woody at the base, rigid and with epidermis peeling off in strips at the base, more or less glabrous but becoming pubescent at nodes and on the inflorescences axis.
Leaf
The leaves are simple, opposite, decussate and carried by a pubescent petiole of 2 to 5 cm long. The blade is elliptical to oval, 1.5 to 2.5 cm long and 0.6 to 1.2 cm wide. The margin is coarsely serrated. The apex and base are pointed. Both sides are covered with short, dense hairs (indumentum). Venation is pinnate, arched.
Inflorescence
False terminal spikes of 7 to 20 (30) cm long, consisting of small whorls of 6 to 10 sub-sessile flowers (pedicel of 1 to 4 mm), at the end of pubescent secondary branches.
Flower
At the base of flowers is a sessile, oval bract, of 3 to 12 mm long and 1-7 mm wide, acuminate and deciduous. Small white flowers sometimes pink or carmine red with a tubular calyx with two small (2-3 mm), pubescent lips. The upper lip is rounded and bends sideways while the lower lip has 4 shorter tines shorter than the upper lip. The corolla form a tube of 3.5 to 5 mm which ends in a large ventral, round and pubescent lip and a very short, truncated dorsal lip, with 4 tines. Four long stamens with white filament and yellow anther long exceeds the corolla tube as well as a long white style shortly bifid top. Ovary superior with 2 carpels, each with two loculus.
Fruit
The fruit consists of 4 small sub-globular dry nutlets, 1.5 mm long, rough, brown, remaining included in the persistent calyx.