Digitaria horizontalis Willd.

Northern Cameroon: The first sprouts of Digitaria horizontalis start in May, when the rains become abundant. The germination takes place even in the absence of tillage. The germination stage lasts until early July. Weeding and mounding can cause new germination phase until mid-August by the rise of seeds at the surface. Flowering occurs very quickly and the first seeds are formed after 4-6 weeks of vegetation. Dissemination period lasts until early November. When the rainy season is over, the plant dries. Weeding and mounding delay the development of the population and seed production, which takes place from mid-September to early November.
Mayotte: Digitaria horizontalis flowers and fruits from December to February.

Digitaria horizontalis has a very broad ecological amplitude. It is a ruderal species and a very common weed.

Comoros: Ruderal plant, characteristic of acid soils, common in all parts of Grande Comore and Anjouan to 1000 m altitude.
French Guiana: Small ruderal very common in non-flooded environments: gardens, roadsides and embankments of the Mana polder. Typical species of herbaceous vegetation in orchards with permanent plant cover.
Madagascar: ruderal species and very common weed in all regions of Madagascar. It is particularly aggressive in the hot zone of low and medium altitude especially in old plots. Aloft (Central Highlands), rather it is replaced by two species affine D. divaricata and D. ciliaris (or D. sanguinalis in the region of Antsirabe) also important.
Mauritius: Weed common in sugar cane fields and fallow in different parts of the island.
Mayotte: Digitaria horizontalis is an exotic species, commonly naturalized in degraded environments, in particular wastelands, cultures, gardens and villages.
Reunion: Common species in the grassy lawns of the North East coast of the island.
Seychelles: Species observed at all altitudes, prefers sunny places.

Global harmfulness

Widespread in upland and hydromorphic areas in the savanna and forest zones of Africa (Mallamaire, 1949; Johnson, 1997). It is capable of rapid growth and has become a dominant species in intensively cultivated fields (Johnson, 1997). Digitaria horizontalis was observed to replace Imperata cylindrica over five years of rice cropping following fallow in Côte d'Ivoire (Johnson and Kent, 2002).
 

Local harmfulness
 
Benin: frequent and scarce.
Burkina Faso: rare but abundant when present.
Northern Cameroon: Digitaria horizontalis is present in 65% of the plots in Sudano-Sahelian region (600-800 mm rainfall) and in over 90% of the plots in the Sudanese region (over 1200 mm rainfall). Very abundant on ferruginous soil, it grows on almost all soil types. It is however very rare on vertisols, the clay content is more than 50%. It is favored by crop intensification, especially by tillage. Sun-loving species, it is much more common in the beginning of the crop cycle. It is considered a major general weed.
Comoros: A weed common in old cassava, banana and sugar cane crops.
Ivory Coast: common and scarce.
Ghana: rare but abundant when present.
French Guiana: D. horizontalis is a species very frequently encountered in fruit and vegetable growing. It is frequent and abundant.
Madagascar: It is a weed important in the major agro-ecological regions of the Great Island: species of high frequency (40% in the Middle East, 60% in the South West) and abundant often forming a stand of variable dimension in cultivations of maize, cassava, upland rice, peanuts. Because of its rapid growth, it can completely suffocate crops if weeding is not done at the right time. Two weeding are often necessary to eliminate competition from the weed.
Mauritius: very common weed in sugar cane fields, very harmfulness when present in large numbers; It is the same in vegetable crops. Its control is usually quite difficult.
Mayotte : Digitaria horizontalis is a very frequent weed in Mayotte, it is present in 23% of cultivated plots, mainly in vegetable and fruit crops. It can also be found in fodder crops. It grows especially in the north of the island.
Reunion: slightly harmful species in the plots receiving tillage. It is present along edges of field or in cover crops lawns.
Seychelles: serious weed or principally in a wide variety of crops, particularly fruit trees, vegetables and ornamental plants.
Chad: frequent and scarce.

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