Saldinia can be recognized by its generally slender shrub habit; tissues with raphide crystals; persistent, interpetiolar, triangular stipules; leaves often in a rather distichous arrangement along the stems; axillary, mostly sessile, glomerulate to subcapitate, few-flowered inflorescences; small four-merous flowers; tubular to salverform white corollas with the lobes valvate in bud; bilobed stigmas and two-locular ovaries with the ovules solitary and basal in each locule; small drupaceous fleshy fruits that are often bright blue and generally develop only one pyrene, which is bony and contains a single seed. The flowers appear distylous at first glance but were documented by Bremekamp (1957) to be unisexual on dioecious plants. Saldinia includes 21 species in Madagascar plus 1 species, Saldinia boiviniana (Baill.) Bremek., in the Comores. The center of species richness is the littoral forests of eastern Madagascar, with several species also found in nothern Madagascar. Saldinia axillaris is the most commonly collected species; Saldinia subacuminata and Saldinia proboscidea are also frequently collected.
Saldinia was studied by Bremekamp (1957). The plants are generally reduced and many species are very similar to each other, in particular with similar inflorescences and flowers. Bremekamp distinguished most of the species based on vegetative characters, mainly leaf shape, size, and dried color, and several of his species delimitations seem unsatisfactory when applied to more recent collections. Most species of Rubiaceae include more variation in these characters than Bremekamp described for the species he delimited, although in some cases the specimens he annotated show additional variation (e.g., Saldinia proboscidea). And, the species he delimited by these vegetative characters appear to be too broadly circumscribed in some cases (e.g., Saldinia axillaris, Saldinia subacuminata), with probably more than one species included and likely also plants that belong to the same species separated in Bremekamp's delimitations.
Saldinia is similar to Lasianthus in general aspect and many details; Lasianthus differs in its bisexual flowers, 3-6-merous flowers, 3-9-locular ovaries, and fruits with 3-9 pyrenes. Lasianthus is found in tropical Asia, Africa, and the Americas, but not in Madagascar. These two genera are closely related, and are today classified together in the tribe Lasiantheae (Bremer & Eriksson, 2009). For some time however these genera were considered closely related to Morinda, which has bilocular ovaries and multiple fruits with two pyrenes per flower. The identity of one Madagascar name in this group, Morinda lastelliana Baill., is not yet clear and this may be a species of Saldinia.