The genus Ladenbergia is classified in the Tribe Cinchoneae, and includes at least 35 species of trees and shrubs that are native to wet forests in the the lowlands and mountains of southern Central America and South America, through Amazonia, the Guianas, and Bolivia to southeastern Brazil. The trees have showy white flowers and dry capsular fruits with flat, papery seeds that disperse on the wind. Many of the species are found in the Andes and adjacent lowlands of Ecuador and Peru and have somewhat restricted ranges, but a few species are distributed quite widely. In particular L. amazonensis and L. lambertiana are found across the northern and central Amazon basin, and L. oblongifolia is found along and in mountains from Venezuela to Roraima, Brazil, and along the Andes from Colombia to Bolivia. In contrast several species seem to be endemic to the mountains of western Panama and the sandstone foothills of the Ecuadorian and Peruvian Andes. Ladenbergia is closely related and similar to Cinchona, and the bark of some Ladenbergia species contains some quinine; however no Ladenbergia species have been cultivated commercially as a souce of this drug.

The flowers are clean white and diurnal or apparently at least sometimes nocturnal, and are glabrous and smooth or sometimes a little roughened (papillose) inside the corolla tube. They are apparently pollinated by moths and perhaps butterflies. The flowers are distylous: some plants have only flowers of the long-styled ("pin" form), with the stigma positioned at the top of the corolla tube and the anthers positioned below, inside the tube; other plants have short-styled flowers ("thrum" form) with the reciprocal or opposite arrangement, with the anthers positioned at the top of the corolla tube and the stigmas below, inside the tube. This reciprocal arrangement is believed to promote out-crossing and diminish pollination by the same flower form, by depositing pollen on different parts of the pollinator so that the pollen from the short-styled flowers is transferred to the stigmas of the long-styled flowers, and vice versa. The fruits are dry, rather woody capsules that open to release numerous small, papery, flattened seeds that are dispersed by the wind. In several Ladenbergia species the leaves are more variable in size, shape, and petiole length than average for Rubiaceae, which along with the strong similarity of the stipules among different species often makes identification of Ladenbergia specimens without flowers and fruits problematic.

Ladenbergia has been extensively confused with the related Rubiaceae genus Cinchona. In fact the separation of these was not clear for many years, but Andersson (1997) showed that species of Cinchona have white, pink, or purple flowers that open during the day and are hairy or fuzzy at the top of the tube and on the lobes, while Ladenbergia has bright white flowers that generally open during the night, and are not hairy or fuzzy inside the corolla tube. Otherwise these two groups are difficult to separate. Previously they were sometimes separated by their fruits, which supposedly opened from the bottom in Cinchona vs. from the top in Ladenbergia, but Andersson showed that in fact the pattern of opening varies within both genera so this distinction does not actually work. In general most (but not all) species of Ladenbergia have woody fruit walls, the stipules quickly caducous (i.e., falling off), and a brown or greenish brown drying color on herbarium specimens, vs. stiffly papery capsule walls, the stipules caducous or persisting on a few nodes, and often a yellowish brown drying color; however several species of Cinchona have thick-walled fruits, and Ladenbergia muzonensis has thin-walled fruits, persistent stipules, and a yellowish brown drying color but its glabrous bright white flowers and molecular sequence data show that it belongs to Ladenbergia.

Ladenbergia is still confused with Cinchona in folk taxonomy, and with several other Rubiaceae genera with stipules that are well developed, ligulate, and held erect in bud. In particular Ladenbergia oblongifolia is replacing true Cinchona in general folk knowledge in some areas, and is sometimes being cultivated in place of Cinchona although it contains only small amounts of the quinine alkaloids; however the true Cinchonas have been extirpated from many areas and local people sometimes know only Ladenbergia oblongifolia as the representative of the group.

Ladenbergia was studied taxonomically by Andersson, who presented a synoptic taxonomy of the genus (1997) and a floristic treatment for the species found in Ecuador (1999). These works differ a little, with a few more species recognized in the later treatment.

Author: C.M. Taylor.
The content of this web page was last revised on 15 September 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

• Andersson, L. 1997. Synopsis of the genus Ladenbergia (Rubiaceae). Nordic J. Bot. 17(3): 255–299.
• Taylor, C. M. & R. E. Gereau. 2010. Rubiacearum americanarum magna hama pars XXIV: New species of Central and South American Bouvardia, Hillia, Joosia, Ladenbergia, Pentagonia, and Posoqueria. Novon 20(4): 470–480.
• Andersson, L. & C. M. Taylor. 1994. 162(1–4). Rubiaceae–Cinchoneae–Coptosapelteae. 50: 1–112. In G.W. Harling & L. Andersson (eds.) Fl. Ecuador. University of Göteborg, Göteborg.