Ludwigia octovalvis (Jacq.) P.H.Raven

Global description

Ludwigia octovalvis is a terrestrial herbaceous, annual or perennial plant, erect, reaching up to 150 cm high. Taproot white or brown. Stem is rounded or angled, solid, glabrous or pubescent. Leaves simple, alternate spiral, stalked, more than 2 cm long / wide, hairy on both sides,  margin entire, attenuated or pointed apex, pointed or attenuate base, pinnately veined. Flowers bisexual, solitary, lateral, with 4 yellow petals. The fruit is an indehiscent capsule or that opens irregularly.
 
Cotyledons

The cotyledons are stalked. The leaf blade is broadly ovate, obtuse base to attenuated, margin entire, rounded apex. It is glabrous, with prominent midrib. It measures 4.5 to 5.5 mm wide by 5 to 6 mm long. Its color varies from green to green red.
 
First leaves

First 2 leaves have a petiole of 0.25 to 0.5 mm long, slightly pubescent and a blade widely ovate, 3.9 to 4.9 mm wide and 5.5 to 6.3 mm long, glabrous, pinnately veined, obtuse base, margin entire, apex rounded to apiculate.
 
General habit

Erect, perennial, herbaceous plant, with stump more or less woody at the base or annual, always very branched, measuring 30 cm to 1.50 m (up to 3 m) high. It can measure a few centimeters high and in this case have a prostrate or creeping growth habit. It is a plant with varying pubescence (thin applied hairs to a dense pubescence), sometimes simply localized when young shoots.
 
Underground system

The plant has a taproot system. In flooded areas, it often forms pseudo-pneumatophores from horizontal roots immediately below the surface of the mud.
 
Stem

The sharply angled stem, often woody at the base, bears many spreading branches. It is glabrous to covered with short hairs. Pubescence that can be highly developed to the top of the branches. It is often of a reddish color. Hollow when young, it becomes hard and then more or less woody.
 
Leaf

It is a diffuse foliage plant. The leaves are simple and alternate, linear to narrowly lanceolate, attenuated at the base in a very short or no petiole, pointed at the apex. The margin of the leaf blade is entire. It measures 2 to 15 cm long and 0.3 to 4 cm wide. The upper side is glabrous, reddish green in color, the underside is lighter, more or less pubescent, especially on the midrib. The side ribs are many, then bent parallel to the margin. They are protruding on the underside.
 
Flower

The flowers are solitary, located in the leaf axils. They are 2 to 3 cm in diameter, sessile or almost. Each flower has 4 persistent sepals with lanceolate lobes, 2.5 to 11 mm long, located at the end of a tubiform calyx, 10 to 20 mm long, often puberulous, rarely villous and 4 oboval petals in wedge-shaped, rounded sub-marginate at the apex, a golden yellow, measuring 0.5 to 2 cm long. 2 tiny pointy bracts are present at the base. The 8 stamens are free. The ovary, inferior, is divided into four boxes containing the eggs spread over 2 rows of houses. It is extended by a thick style scarcely exceeding the stamens, topped with a globular stigma.
 
Fruit

The fruit is a cylindrical capsule dehiscent in 8 filiform valves. It is fluted, glabrous pubescent, measuring 1.7 to 5 cm long and 2 to 8 mm in diameter. It is reddish purple when ripe. It contains many seeds over 2 rows per loculus.
 
Seed

The seeds are free, rounded, brown-tawny in color. They feature a raphe as big and it makes them look twice. They measure 0.5 to 0.7 mm in length and diameter.

Origin

Ludwigia octovalvis is native to tropical America.

Worldwide distribution

It is a pantropical species, present in Central America and the Caribbean, South America, tropical Africa, Southern Africa, South-west islands of the Indian Ocean, India, Bangladesh, South-east Asia. It is reported also in China, Indonesia, Australia and the Pacific Islands.

https://www.gbif.org/species/5420987