Galinsoga parviflora Cav.

Brazil: Galinsoga parviflora has a very short development cycle, producing the first viable seeds 4 weeks after germination. There are therefore several generations per year. At the time of production, the seeds are 90% viable. The good temperature for germination is between 10 and 30°C, with alternating temperatures stimulating germination. Seeds on the surface of the soil germinate evenly. Seeds no longer germinate at a depth of more than 2 cm.
China: Galinsoga parviflora flowers and fruits from July to October.

Galinsoga parviflora is a C3 species.

Brazil: Galinsoga parviflora prefers fertile, moist and slightly acidic soils.
China: Galinsoga parviflora grows on streamsides and sparse forests. It is a widely distributed crop weed in China.
Comoros: Galinsoga parviflora is a fast growing plant very common in humid areas and in old vegetable cultivations.
Madagascar: Species relatively common in the highlands. It also invades vegetable cultivations or taro, occupying slightly humid soils bordering the lowland paddy fields in the Highlands or at medium altitude. Species currently being extended, rather frequent and abundant in rain-fed crops in the highlands, and particularly in the region of Antsirabe (volcanic soils).
Mauritius: Widespread weed, especially since the end of last century; it is very common in gardens.
Reunion: G. parviflora is a species that is spreading rapidly. It is particularly well adapted to wet soils, rich in nitrogen, especially at medium altitude between 300 and 1000 m.
Seychelles: absent.
West Indies: Galinsoga parviflora is a cosmopolitan, ruderal and weed species.

Local harmfulness

Brazil: Galinsoga parviflora is sensitive to competition. It only forms dense populations when other species are small and sparse.
Comoros: Galinsoga parviflora is a weed characteristic of vegetable cultivations.
Madagascar: Abundant species. It can hinder the development of vegetable crops if weeding is done late. It is also harmful for corn and beans.
Mauritius: A weed of vegetable crops, it can have a very strong harmfulness when present in large numbers, particularly in lettuce cultivation.
Reunion: This weed, infrequent and rarely abundant in large crop (sugar cane), is mainly a weed of vegetable crops and lens, occurring particularly at medium altitude. It is able to expand rapidly in hot and humid season, it competes very early with crops, until it reaches a full covering if the weed is poorly managed.
Seychelles: absent.
South Africa: Distributed to the north east of South Africa. It is atroublesome in different crops, in high infested areas it can be competitive.

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