Succulent Trees of Eastern Brazil

Daniel L Mahr

We saw over 30 succulent tree species in seven plant families on the CSSA fieldtrip to eastern Brazil. About half were cacti. Here we focus on the non-cacti.

Burseraceae—the frankincense, myrrh, and copal family

With over 500 species in about 17 genera, members of the Bursera family grow mostly in tropical and subtropical areas worldwide and are well known for the aromatic compounds in their sap. Four genera are of interest to those who grow pachycaul plants and succulent bonsai. The two largest of these are the widespread New World Bursera (the source of copal), and the Old World Commiphora (the source of myrrh). The wood of these plants is usually light and soft, and many species indigenous to arid areas have developed the ability to store water in root and stem tissues, giving them a plump appearance. They also tend to have papery peeling bark underlain with green photosynthetic bark, making them attractive both in the field and in cultivation.

Euphorbiaceae—the spurge family

The Euphorbia family is well known to succulent growers, who appreciate the genera Euphorbia, Jatropha, and Monadenium, among others, mostly of African origin. But succulent euphorbias also occur in Brazil. E. phosphorea, for instance, is a large succulent shrub to 3 m tall or more, but with prolific branching from the base and no distinct trunk, it doesn’t qualify as a tree. Cnidoscolus is a spurge genus best known for its nasty stinging hairs. Most are herbs or small shrubs, some have succulent stems, and some almost reach tree stature. Then there’s Jatropha, a genus with nearly 200 species in the American and African tropics and subtropics. We saw several in eastern Brazil growing as small trees, though most were without flowers, fruits, or even leaves in November, and were therefore not identifiable.

Fabaceae—the bean family

With a multitude of vines, shrubs, trees, and herbaceous annuals—the Fabaceae is a huge and varied family. And although common in dry areas throughout the world, relatively few species have developed succulence. One exceptional genus with a few succulent representatives is Erythrina, whose members are commonly called coral trees because of their often red, coralliform inflorescences. The 130 species of Erythrina grow in tropical and subtropical regions worldwide. Trunks, stems, and even leaves characteristically armed with spines, some of these are also soft-wooded or have tuberous roots and can be grown as container plants or trained as bonsai. Two species, Erythrina mulungu and E. velutina, are common to this part of Brazil, and while erythrinas were encountered at Porto Novo, Itinga, and Milagres, the plants were invariably leafless, flowerless, and in some cases without seeds, so species identification was difficult.

Malvaceae—the mallow family

Most people’s foremost image of a succulent tree is the African baobab (Adansonia species). But the Americas have their baobab relatives, too. Cavanillesia is, from the perspective of size alone, the American counterpart of Adansonia. Ceiba (kapok) trees often have a barrel or bottle-shaped trunk and the trunk and branches can be armed with large spines. In Portuguese these trees are commonly called barriguda (“potbellied”). The name Chorisia was previously used for some members of this group. There are at least six species in eastern Brazil, five of which occur in the states of Bahia and Minas Gerais. We saw at least three. The 22 New World species of Pseudobombax stretch from Sonora, Mexico well into South America, with nearly half occurring in Brazil. Pseudobombax are sometimes referred to as shavingbrush plants, referring to the rather large flower, whose five strap-like, dull-colored petals recurve or hang limp behind an erect set of long white stamens. Many species also have an attractively-patterned green trunk, and there is a tendency to stem or root succulence in the genus. Of nine species in Bahia we saw five or six species on our trip.

Moraceae—the fig and mulberry family

We tend to think of figs as rainforest plants, but with over 800 species in the genus it isn’t surprising that some are found in arid or seasonally dry climates. Such species may adapt to rocky areas, and their exposed roots form interesting sculptures on the rock surfaces. Some are caudiciform in youth and would make good succulent bonsai subjects. I saw only one such plant on this trip, in the area of Morro do Chapéu in Bahia. It was a short tree, a bit over 2 m tall, with a well developed caudex growing on rocks.

Velloziaceae

We saw many species of Vellozia on the trip. Virtually every stop was home to one or more species. Generally these are short plants, branched mainly from the base, with rather thickened stems and often with attractive grassy leaves and showy flowers. I include Vellozia auriculata here because it is one of the few giants of the family. To 3 m tall, it resembles an arborescent Yucca, with thickened stems and a flared trunk. I have no idea if it is truly succulent, but it sure plays the part well. V. gigantea is an even larger species (to 6 m) that grows in the same general region of Minas Gerais.