Commelina diffusa Burm.f.

Madagascar: Commelina diffusa flowers and fruits from February to June.
Mayotte: C. diffusa flowers and fruits all year long

Commelina diffusa is an annual to vivacious species. It propagates by seeds and by layering of segments of broken stems. Seeds and stem fragments are spread by water, animals and tillage tools.

Commelina diffusa differs from C. benghalensis L. by the absence of hairs on the margins of the pseudopetiole, by a very elongated spathe, with glabrous faces and an unwelded back. The first flowers are long pedicelled.

Commelina diffusa subsp. scandens differs from C. diffusa by its larger size, more robust appearance, with pubescent internodes and sheath, linear leaves and ventral fruit lodge 3 mm long, and dull purple (Madagascar) to bright blue (Southern Africa) flowers; whereas C. diffusa is smaller and less robust, with glabrous internodes and sheath, lanceolate leaves and the ventral fruit compartment is 1 to 1.5 mm long, the flowers are bright blue, the outer petal less colored. Moreover, C. diffusa subsp. scandens is mainly a species of humid to flooded environments while C. diffusa grows in dry as well as humid to flooded environments.
In Madagascar, C. diffusa subsp. scandens is a ruderal species and a common weed of wet places all over the island while C. diffusa is a dominant weed in the dry semi-arid zone of the southwest.

Commelina diffusa is commonly found in moist fields, along ditches, on waste land and under bamboo, on soils rich in clay or humus, from sea-level up to 2000 m altitude.

Comoros : Commelina diffusa is present in the three islands in shaded and humid environment, especially in the zones of low altitudes until 800 m.
Madagascar: This species grows in alluvial soils, ferruginous soils and humus-bearing ferralitic soils, fairly fertile in sunny or lightly shaded areas. One meets it at the edge of the ways and the cultures. It is a weed of semi-intensive rainfed crops (rainfed rice, maize, cotton, groundnut, vegetable crops) in almost all agro-ecological zones of Madagascar.
Mauritius: Common species developing in general in humid station.
Mayotte: C: diffusa is a common native species in a wide range of open or secondarized wetlands, in marshes, river and lake banks, ditches, crops, wastelands, gardens, roadsides, urban areas.
Reunion: The species develops on deep soils, in shaded and fresh, even humid situation. It is generally localized in the littoral zones or of average altitude.
Seychelles: Species of clearings and abandoned places. It is rarely abundant.
West Indies: The abundance of Commelina diffusa is closely linked to humid, shady conditions and intensive agricultural practices (absence of fallow land, rotations, repeated chemical weeding, heavy fertilisation, etc.). It does not compete well with other grasses and becomes less abundant in plots with a high floristic diversity.

Local harmfulness

Benin: rare and not very abundant.
Burkina Faso: rare and not abundant.
Chad: rare but abundant when present.
Comoros: Commelina diffusa is a weed that is present in all crops.
Côte d'Ivoire: frequent and generally abundant.
Ghana: rare but abundant when present.
Madagascar: C. diffusa is a frequent and locally abundant weed in sub-humid or semi-arid production areas. It is a particularly damaging species in cotton cultivation (southwest) because of its rapid vegetative (and seed) propagation due to its succulent stems that resist desiccation after weeding.
Mali: Rare but abundant when present.
Mauritius: A fairly rare weed in crops, with low to medium pest pressure.
Mayotte: C. diffusa is a weed present in 7% of cultivated plots, particularly in ylang crops in the north of the island.
Nigeria: frequent and generally abundant.
Reunion: C. diffusa infests both sugarcane fields and vegetable, pineapple and lentil crops. It is infrequent (Fr < 30%) and not very abundant, and therefore does not present any particular problem in cultivation. Its biology is very similar to that of C. benghalensis.
Senegal: rare and not very abundant.
Seychelles: A weed with low nuisance value.
Tanzania: frequent and not very abundant.
Uganda: rare but abundant when present.
West Indies: Commelina diffusa is a weed that causes little damage to sugarcane crops. On the other hand, it is locally abundant in banana plantations, vegetable and food crops in rainy areas where it is difficult to control when it forms a significant cover. This species constitutes an agent of dissemination of the cucumber mosaic virus (CMV), which is particularly damaging to a large number of fruit, vegetable and food crops (characteristic symptoms: chlorotic mosaic of the leaves and deformations of the leaves, flowers and fruits, as well as a "stunting" of the infected plant)

Medicinal: In Peninsular Malaysia, the leaves are widely used for poulticing sores. In Indonesia, the crushed leaves and stems are used for irregular menstruation. Dirty wounds are poultice with the mucilage from the stems. In some areas, leaves are used as an ointment and absorptive. Leaves are used as an abortifacient, also used against infected wounds.
Food: The leaves are edible and may be used as a vegetable. 
Animal feed: In Comoros Commelina diffusa is used as a fodder species.

Global control

Cultivation: It is particularly difficult to control by cultivation, partly because broken pieces of above and below ground stems readily take root. With hand weeding, it is necessary to uproot all the plant from the soil to ensure effectiveness.
Biological control: Very few natural enemies have been reported to attack C. diffusa and, of this, only two agromyzid leaf miners from the Americas appear promising (Amauromyza sp. and Liriomyza commelinae from Diptera family).
Chemical control: Post-emergence application of 2,4-D at 500 g/ha.

Management recommandations for annual broadleaf weeds in irrigated and lowland rice in Africa, see: http://portal.wiktrop.org/document/show/20

Management recommandations for vivacious broad-leaved weeds in rice fields: http://portal.wiktrop.org/document/show/26

Local control

Madagascar: In Madagascar C. diffusa is controlled only by manual weeding.

Herbarium pictures ReCOLNAT: https://explore.recolnat.org/search/botanique/simplequery=Commelina%2520diffusa