The MO specimens are on loan so the identifications have not been all recorded, and the distribution given here is provisional. This species has been collected rather frequently in Madagascar, though it can be easily overlooked. Plants of Oldenlandia corymbosa are generally small, often prostrate herbs and frequently grow in cracks in roadside pavement or concrete, particularly in areas or at least microsites with a good and regular supply of water. Oldenlandia corymbosa has been collected on both lateritic and sandy substrates, and is particularly commonly encountered around human constructions including houses, roads, and on bridges. This species is adventive world wide in wet tropical areas, and no doubt is also naturalized in the Comores, Seychelles, and other areas near Madagascar though this is not yet documented.

Several varieties of Oldenlandia corymbosa have been separated by Bremekamp (1952) and Verdcourt (1976). In particular, var. caespitosa has been separated based on having more reduced inflorescences, with only 1 or 2 flowers borne on each peduncle vs. 3 to 4 in var. corymbosa and some others varieties. Several of these other varieties were separated based on having the leaves all relatively narrow, rather than some or all of them wider, and var. linearis was characterized as having a robust habit while var. nana was separated based on reduced size of the entire plant. However these characters are most often correlated with microsite (pers. obs.): plants that grow in cracks in pavement where people and animals walk on them are predictably smaller than those that grow in more protected sites and fall into var. nana, while plants that grow in exposed areas in general have narrower leaves than those in more shaded sites. Thus these differences do not seem to characterize separate evolutionary lineages, and thus these varieties do not seem meaningful. Both var. corymbosa and var. caespitosa have been documented in Madagascar, though these forms also seem more strongly correlated with microsite than separate evolutionary trajectories.