Ludwigia adscendens (L.) H.Hara

Global description

Ludwigia adscendens is a creeping or floating aquatic herbaceous plant. The creeping stems can reach up to 6 m long. Floating stems bear beams of roots converted into white spindle-shaped floats, emitted at the nodes. The leaves are simple and alternate, located on the emerged stems. They are elliptic oblong to linear lanceolate. The solitary flowers ranging in color from yellow to white, are located on the upper leaf axils. The calyx is in the form of a long tube containing the ovary and surmounted by five sepals. The fruit is a woody capsule more or less cylindrical equipped with 10 ribs. It is reddish brown in color. It contains many small light brown prismatic seeds, included in a corky endocarp.
 
Cotyledons

The cotyledons are stalked and glabrous. The petiole is 1.5 to 2 mm long. The elliptical blade is 4.5 mm long and 2.5 to 3 mm wide. It is characterized by the presence of a marked midrib of an entire margin, an attenuated base and an apex rounded to slightly notched.
 
First leaves

The petiole measure 0.5 mm long. It is glabrous or weakly pubescent, with 2 tiny stipules at the base. The lamina is glabrous to pubescent, elliptical, margin entire, obtuse to attenuated base, apex rounded to slightly emarginate. It is 3.5 mm long and 2.8 mm wide. It has a pinnate venation.
 
General habit

Amphibious perennial herbaceous plant, aquatic or sub-aquatic, creeping on wet soil or floating on the surface of the water with the end of the stems erect.
 
Underground system

Floating stems bear three kinds of roots: fines long axillary roots that enter the mud, red or black dangling aquatic roots that bear numerous short spread out rootlets , floating fusiform roots (pneumatophores) spread, 1-6 cm long, white or pink, spongy and  airing grouped in whorls on floating rods at the nodes.
 
Stem

The cylindrical stems, hollow, erect, fleshy often red. They measure up to 1 m high, horizontal stems up to 6 m long. They are usually glabrous except for the end of the erect portion which can be strongly pubescent, but in case of drying of the region, the plants can survive on dry soil and thus in this case they are densely pubescent and the flowers are rare.
 
Leaf

The leaves are simple, alternate, are helically arranged around the stem above the water. Tiny stipules are present, located at different heights. The lamina is oblong, narrow elliptic to obovate, margin entire, acute, obtuse or rounded or even notched apex, base attenuate into a distinct petiole of variable length (1-18 mm). They measure 0.4 to 10 cm long and 0.7 to 4 cm wide. They are glabrous to slightly pubescent on both sides, satin green when they are glabrous, with arched lateral veins paler. Leaves, shorter and wider with rounded top.
 
 
Flower

The solitary flowers are arranged on the axils of upper leaves. They are bisexual, long stalked and open only during one day. The tubular calyx pubescent, sometimes glabrous, 10-13 mm long has 5 oblong-lanceolate sub-persistent lobes, 7-9 mm long.  The 5 obovate, rounded and emarginate petals are 8 to 20 mm long and 8 to 12 mm wide. They are deciduous. Their color varies from creamy white or very pale yellow with dark yellow to bright yellow base. The stamens are 10 in number. The inferior ovary consists of 4 to 5 cells with many eggs arranged in single rows. The white style measures 6 to 8 mm, densely villous in its lower half. It is topped with a globular green stigma.
 
Fruit

The fruit is a capsule with 5 loculus, elongated, more or less cylindrical, 1.2 to 3.5 cm long and 3 to 4 mm in diameter, often slightly curved. It is surmounted at the apex by the calyx. It is woody, glabrous or has long soft bristles. Reddish brown in colour, it is marked by 5 darker ribs and 5 rows of bumps. It hangs towards the water at maturity. The numerous seeds are arranged in a row in each loculus. The endocarp splits in corky disks that surround each seed.
 
Seed

The prismatic seed with 4 corners, measuring 1.3 to 1 mm long. It is pale brown in colour.

Worldwide distribution

Ludwigia adscendens occurs in many tropical regions such as tropical and continental Southeast Asia, tropical Africa, Madagascar, Reunion, Mauritius, South America, Central America and the USA, as well as in Oceania (Australia, New Zealand). It is also present in several European countries.

https://www.gbif.org/species/7322187