Trema is a genus of about 15 species of evergreen trees closely related to the hackberries (Celtis), occurring in subtropical and tropical regions of southern Asia, northern Australasia, Africa, South and Central America, and parts of North America. They are generally small trees, reaching 10 - 20 m tall.

Taxonomy

Previously included either in the elm family, Ulmaceae, or with Celtis in the Celtidaceae, genetic analysis has shown the Celtidaceae are best placed in the hemp family, Cannabaceae.

Description

The leaves are alternate, simple, 7 - 15 cm long, ovate-acuminate to lanceolate with a long pointed tip, and evenly serrated margins. The fruit is a small drupe 3 - 5 mm in diameter.

Species associations

Trema species are sometimes used as food plants by the larvae of hepialid moths of the genera Aenetus, including A. splendens, which burrow horizontally into the trunk then vertically down, and Endoclita, including E. malabaricus. Some Trema species unusually able to live in symbiosis with rhizobia for nitrogen fixation as a non-legume. In this case it is customary to mention these species as a separate genus Parasponia.

Uses

Trema orientale is widely planted for land reclamation in southern Asia, valued for its tolerance of poor soils due to its ability to fix nitrogen. It is also an invasive species on some Pacific Ocean islands.

Species

Trema comprises the following species:

Species names with uncertain taxonomic status

The status of the following species is unresolved: