Global description
Trianthema portulacastrum is a fleshy, prostrate to weakly erect plant, with numerous basal ramifications. It can reach 30 to 50 cm high. The stem has a line of hairs on surfaces exposed to light.The leaves are simple, opposite, entire but of unequal size (a large opposite a small). Twigs and flowers always grow at the base of the small. The lamina is obovate in shape, fleshy. The flowers are solitary, included in the base of the petioles and star shaped, white to pinkish white in colour and very small. The fruits are small capsules, the seeds are lenticular, brown to black in colour.
Cotyledons
Elliptical lanceolate cotyledons, petiolate, of unequal size, one is 12 to 16 mm long and 3 to 4 mm wide, the other is 10 to 12 mm long and 2 to 3 mm wide, glabrous and fleshy.
First leaves
First leaves opposite, simple, with the distinction of having a small leaf opposite a large, alternating. The petiole is short, flared in sheath at the base. The lamina is rounded elliptical, glabrous, and fleshy. Stipular collar adorned in the middle with an expansion acuminate as from the second pair of leaves.
General habit
Herbaceous plant, quite fleshy, prostrate to ascending and much branched, developing in patches.
Underground system
The plant has a taproot system.
Stem
Cylindrical stem, solid, fleshy, having a line of hairs on the face exposed to light. The stems may reach up to 1 m long. It is often tinged with purple. The ramifications emerge from the axils of the leaf of each pair.
Leaf
Leaves simple, opposite, stalked. At the base of the petioles is a stipular collar topped with a large tine in the middle. The leaves of the same pair are of unequal size. The large leaf is carried by a petiole, 1 to 2 cm. The lamina is widely obovate, elliptical or orbicular, 2 to 4.5 cm long and 1 to 3.5 cm wide. The base is wedged or sometimes rounded, progressively tapered, the apex is rounded, notched or apiculate. The margin is entire to slightly undulate. The leaf is almost sessile, elliptical, with acute base and apex. The faces are glabrous.
Inflorescence
Flowers solitary, sessile, in the axils of the small leaf, more or less included in petiole sheath.
Flower
Flower formed of a calyx in tube at the base and topped by 5 to 6 oval or lanceolate lobes, white to pink purple on the inside, 3 to 5 mm long, having a sub apical dorsal mucron. The corolla is absent, 15 to 20 stamens are inserted at the top of the tube of the calyx. The ovary is surmounted by a single linear style.
Fruit
The fruit is a dehiscent obconical capsule, 4 to 5 mm long, opening in lid. The capsule contains 2 to 8 seeds.
Seed
Lenticular seed, spiral, ending in a spout, 2 mm in diameter. Tegument is tuberculate, reddish brown to black in colour.
