Costus
Costus dubius (Afzel.) K.Schum.
Costus dubius is a terrestrial herb in the Costaceae family, native to parts of Africa and cultivated in greenhouses, where it often sets seed and outcompetes other species. It grows in a range of habitats, from primary rainforests to swamp forests and plantations, at elevations of 0–1400 m. It flowers and fruits throughout the year. The plant is characterized by its glabrous leaves, white to cream corolla, and a white labellum with a yellow nectar guide. Inflorescences typically terminate a separate leafless shoot and are composed of 1-flowered bracts. Some specimens exhibit a long ligule, and the species is distinguished from C. afer and C. dinklagei by specific morphological traits.
Description
Costus dubius is a terrestrial herb reaching 0.5–3 m in height. It has glabrous leaves with narrowly elliptic lamina, 15–36 cm long and 6–12 cm wide, and a leaf sheath 0.5–2 cm in diameter. The ligule is chartaceous, truncate to 2-lobed, 3–30 mm long. The inflorescence is ovoid to ellipsoid, 5–30 cm long, and terminates a separate leafless shoot, 5–100 cm long. Bracts are green with reddish margins, 1.5–3 cm long, and coriaceous. Flowers are white to cream, 25–55 mm long, with a funnel-shaped labellum, 35–40 mm long, marked by a yellow nectar guide. The species is found in diverse habitats, including primary and secondary forests, along rivers, and in plantations, and is often cultivated in greenhouses where it readily produces seeds and outcompetes other Costus species.
Other common names
Costus
Distribution
Hawaii · Angola · Burkina · Burundi · Cameroon · Central African Repu · Congo · Equatorial Guinea · Gabon · Ghana · Guinea-Bissau · Gulf of Guinea Is. · Ivory Coast · Kenya · Liberia · Malawi · Mali · Mozambique · Nigeria · Queensland · Senegal · Sierra Leone · Sudan · Tanzania · Togo · Uganda · Zaïre · Base-Guinée · Guinée forestière · Haute-Guinée
Synonyms
Costus afer var. maculatusCostus albusCostus littoralisCostus maculatusCostus zechiiZingiber dubium
