Costus guanaiensis

This page is for the "new" C. guanaiensis that produces small bract appendages and red flowers. Paul Maas had proposed to describe and publish a sp. nov. to be called Costus bolivianus, but then realized that the type specimen from Guanay, Bolivia that was described by Rusby as C. guanaiensis was actually this form and not the form we have all come to know as C. guanaiensis.

This was originally described by H. H. Rusby in the Torrey Botanical Club Bulletin, Vol. 29, in 1902, named there as Costus guanaiense. In his description, Rusby described the bracts as being "about 5 cm long, 3 cm broad, thick, rigid, brown, strongly nerved, the foliaceus tips about 1 cm long, and 6 or 7 mm broad , obtusish, appressed or reflexed at the tip". He did not include any information about the flower. The type was his collection No. 2225 at Guanai (now usually spelled Guanay), Bolivia, collected in May 1886.

Schumann included this species in Englers, Das Pflanzenreich, Vol. IV, 1904. He changed the species name from C. guanaiense to C. guanaiensis. He basically repeated the same description, translated into Latin, and did not include any description of the flower.

In 1934 in Phytologia, Vol. 1 No. 2, page 50, Rusby described another species from Mapiri, Bolivia (Tate 442) which he called Costus longifolius, described as having a slender stem, leaves to 25 cm long by only 4 cm wide, lanceolate to oblanceolate in shape. He described the bracts as "scales", spreading, ovate, 5 cm by 2.5 cm with a "broad base and acute summit". Again, he did not give any information about the flowers. Dr. Maas believes this to be a synonym to this reconfigured species, and I agree.

Plants that we have determined to belong to this new characterization of the species Costus guanaiensis have very distinct and unusual looking flowers. They are basically red flowers, more or less tubular in shape, and with distinctive labellum and corolla lobes. The labellum is almost flat with reflexed margins. The corolla lobes are triangular shaped and tend to fan out from the flower. I first saw this species in Peru at two locations in the Manu Area of Madre de Dios and bordering parts of Cusco department. I have also seen it farther to the south in Madre de Dios Tambopata area, in Cusco at Quincemil and and in Puno. My observations of this newly described Costus guanaiensis may be found at the Inaturalist link above.

HORTICULTURAL NOTES:
There is a plant of this species in cultivation that was collected many years ago by Mark Collins and Alan Carle from southern Peru, and sold as Costus 'Red Feathers'. I visited in Puno, Peru, near the town of San Gabán and found the same form there - the likely locality where 'Red Feathers' was collected.

ACCESSIONS:Click links (if any) to see details of individual collections. R3263- R3429-

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