Alluaudia ascendens

Native to southern Madagascar, this succulent tree grows in dry shrubland and can reach about 33 to 43 feet tall in its natural habitat. A thick trunk supports a few narrow upright branches, with conical spines arranged spirally along the stems. Its small leaves are deciduous. Clusters of white to reddish flowers appear near the ends of the stems; male flowers have numerous stamens, while female flowers have a short style ending in three red stigmas. The species is vulnerable in the wild. Photographed in Florida.