In my website at www.gingersrus.com I have divided the Costus species between the African species and the neotropical species. The African species have not been well studied up to now, and there are only the floras of various single countries available as a good reference describing the species. Dr. Paul Maas who compiled the monograph on the neotropical species in the 1970's is currently working on a monograph for the African species.
Costus afer is an African Costus that is unusual in that it commonly flowers both at the base and terminally on a tall leafy stem. It is also distinguished by the fact that it produces two flowers per bract instead of one flower per bract as in most African Costus and all the neotropical plants. It is superficially similar to Costus dubius which produces only one flower per bract.
Costus afer is not hardy in areas with freezing winter temperatures and must be grown in a greenhouse in places colder than zone 9-B. It grows to a height of about 8 feet.