There are an estimated 400 species in this genus, all native to tropical and subtropical Asia, Africa, and Australia.

[2][3][4] They are dioecious,[5] mostly leaf-climbing lianas with slender, reedy stems.

To aid scrambling some species have evolved hooks on the underside of the midrib, or more commonly by modified "pinnae" or tendrils in the form of stout, backward-pointing spines.

[6][7] The fruits of certain species, in particular Calamus draco, produce a red resin known as "Dragon's blood".

[8] As of April 2022[update], Plants of the World Online recognises 415 species:[1] The stems may be harvested for their cores, which are used for everything from canes to furniture.