In the aquatic flora of Brazil, the genus Ludwigia presents ca. 48 species. Ludwigia species are mostly helophytes and exhibit great phenotypic plasticity, which makes their identification difficult. The objective of our work was to analyse diagnostic characters that are of importance for the delimitation of Ludwigia species occurring in the Recôncavo basin of Bahia. Collections were made from 2013 to 2016. Morphological analysis was carried out using material collected in the field and specimens studied in several Bahian herbaria. Five species were found for the Recôncavo of Bahia: L. erecta, L. hyssopifolia, L. leptocarpa, L. octovalvis and L. peploides. An identification key, descriptions, photos and taxonomic comments are presented. The following fruit and seed characters were considered as the most important diagnostic features: ovary characters, ovule shape and placentation types, seed shape, dimensions, colour, endocarp and raphe.
endocarp; fruit; aquatic plants; raphe; seed.