Apodanthera—Two caudiciform cucumbers from Bahia, Brazil

Marlon C Machado

The cucumber family (Cucurbitaceae), with some 900 mostly tropical species, is a family of mostly climbing or trailing, usually perennial herbaceous plants with a worldwide distribution in tropical and to a lesser extent in subtropical and temperate areas of the world. A number of species are of great economic value as food plants—pumpkins and other squashes, melons and cucumbers—and others are used as medicine. But for the grower of succulent plants, the most interesting species are those from arid and semiarid regions that develop a caudex. Tropical Africa and Madagascar are particularly rich in species of interest to collectors (Cephalopentandra, Coccinia, Corallocarpus, Cyclantheropsis, Gerrardanthus, Kedrostis, Momordica, Odosicyos, Trochomeriopsis, Xerosicyos, and Zygosicyos), and in North America the most well known caudiciform species belong to Ibervillea and Marah. But little is known of the South American caudiciform Cucurbitaceae, of which Apodanthera is a representative.

Apodanthera was described in 1841 and was last revised in 1916. Recent accounts cite between 15 and 25 species, the majority in Brazil, though the best-known is Apodanthera undulata of United States Southwest and Mexico, where it is known as Coyote Melon or Melón Loco. It develops an underground caudex up to one meter in diameter. There are eight species of Apodanthera in the state of Bahia, Brazil. Some of these species develop an aboveground caudex up to six inches (15 cm) in diameter, and as the bases of the vines are not deciduous, with time they thicken to become one inch (2.5 cm) or more in diameter.

During the CSSA field trip in Brazil in June 2008 we found Apodanthera congestiflora and A. villosa in flower and fruit in the central Bahia town of Morro do Chapeu. The two grew together at a site about 22 km to the west of Morro do Chapeu (where A. villosa is endemic), and a large population of A. congestiflora was found 16 km southwest of the village Olhos D’água do Fagundes towards the cave Gruta dos Brejões. Both species grow in sandy soil, usually at the base of spiny shrubs, which afford some protection to the caudex, though sometimes the plants are found in the open. The vines climb the surrounding shrubbery in order to reach the sun, and when without leaves are rather inconspicuous.

These two species are similar when out of flower and fruit: both have trifoliolate leaves (divided in three leaflets) that are pubescent on both faces, and each has a rounded to oblong aboveground caudex about two to four inches (5–10 cm) in diameter with brown to dark gray bark. But with careful observation they can still be distinguished. A. villosa has vines whose epidermis is glabrous (meaning without hairs), glaucous, and often bright orange when exposed to the sun, whereas vines of A. congestiflora have a finely pubescent (hairy) epidermis, green but soon developing a brown bark. While these characteristics are useful to distinguish the two species at Morro do Chapeu, they are not unique, and related species share some the same characteristics. The best way to positively identify the species is to observe their flowers and fruits.

CSSA members can read more about these plants and their cultivation in our special issue on eastern Brazil.