Photo: R. Pérez
Description: A medium-sized tree with a straight trunk that is often unbranched, with just one cluster of leaves at the top of the trunk (like a palm). In big trees, though, there are a few large branches, each with a cluster of leaves at the end. Leaves are very large -- no other tree in the area other than palms -- has larger leaves. They are toothed, long, narrow at the base, and broad at the apex.
photos: leaf... fruit... flower... flower... flower... bark... leaf... fruit... leaf-flower... seedling... seedling...
drawings: all parts...
Drawing: R. Pérez
Flowers and fruits: Flowers are large and purple, with many stamen arranged in a ring, few in number. From March to June, when they are mature, a few flowers can easily be found on ground beneath adult trees. Fruits are round, green, hard, larger and heavier than a baseball. Inside are a few large seeds. The fruits often remain on the ground for weeks, rotting and collecting mold. Agoutis eat the seeds, but they also bury some for later use and thus serve as dispersal agents.
Distribution: An abundant tree in secondary forests in the central part of the isthmus, less common at Sherman, and not seen in forests near Panama City or at the wettest Caribbean sites. At Plantation Rd near summit, around Gamboa, along Pipeline Rd out to the Rio Limbo, and at Barro Colorado this species is the dominate secondary forest tree. In some sites, Gustavia makes up 50% of the canopy. Anywhere in the central part of the isthmus it is a good indicator of forest that has been regenerating for 60-100 years. It is much less common in old-growth, and does not typically form the earliest regeneration. It is also fairly common in abandoned pastures, apparently because agoutis take the seeds out into the fields, and because the very large seeds allow seedlings to germinate in harsh pasture conditions.
How to recognize: The long leaves in a single cluster at the apex of a large branch or trunk are unmistakable. In the center part of the isthmus, there is just one other species that is similar, Cespedezia macrophylla. The two species are unrelated, and have completely different flowers. But without flowers they are easily confused, and both are common along Pipeline Rd. Indeed, a prominent publication in Science years ago was based on mis-identification of Cespedesia and Gustavia at Pipeline Rd. With a fallen leaf in hand, look closely at the leaf underside -- the smallest veins of Cespedesia are prominent and parallel, whereas in Gustavia they are inconspicuous and widely spaced. On the trees, Gustavia leaves tend to droop downward much more than Cespedesia leaves, some of which point upward, and new leaves of Cespedesia are conspicuously red, unlike Gustavia. There are other relatives of G. superba in the area -- G. fosteri, G. dubia, and LK griaca Grias cauliflora.