This page contains photos and description of a species, form or cultivar of Costaceae.

Gingersrus Database Taxon ID 7830

Costus obscurus


OLD NAME: Costus sp. nov.

NEW NAME: Costus obscurus

NAME CHANGE NOTES: New species published March 22, 2023 in PhytoKeys 222: 75-127, has been confused with 'El Whiskey' and with C. acreanus.

FULL SCIENTIFIC NAME: Costus obscurus D.Skinner & Maas

STATUS : sp. nov.

CONTINENT: Neotropical

FIELD OBSERVATIONS:(If field observations are available, you can click on the link to open in a new window.)
FIELD OBSERVATIONS

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SYNONYMS:


BOTANICAL NOTES:
Costus obscurus was published March 22, 2023 in PhytoKeys 222: 75-127 by Dave Skinner and Paul Maas. I first saw this plant growing in the wild at Pantiacolla Reserve in Madre de Dios, Peru in 2014. It was growing in deep shade and muddy soil and looked very much like a collection from Tim Plowman via John Kress and the Tingo Maria Botanical Garden, that was growing at the Smithsonian Greenhouses, USBRG 1994-657. This collection had caused much confusion as it had somehow become confused with a Colombian collection, also by Plowman, known by the cultivar name 'El Whiskey'. The compact shape of the plant with its dark green upper side leaves and deep purple undersides gave a similar appearance from a distance, but the Peruvian plant is densely hairy among other differences.

In trying to determine the correct identity, there was further confusion when it was incorrectly identified as Costus acreanus. Then in November 2016 during my trip to Huanuco, Peru, I visited an area a few kilometers west of Tingo Maria and came across the same species, growing in a deeply shaded area along a muddy quebrada, and looking identical to the plant Plowman had collected 65 kilometers to the north in Department San Martin and deposited at the Tingo Maria Botanical Garden. Detailed photographs and measurements were taken.

I also saw this new species growing in Pasco, Peru in 2017, but it was not until January 2020 when I visited the region along the Rio Acre in western Brazil, and discovered the true form of the species Costus acreanus, that I realized that this was a completely different species that had never been named and described. I drafted a description and named the species Costus obscurus to reflect both the very dark green and purple leaves, and the dark shady habitat, as well as the obsure (English language meaning unclear, uncertain, unknown, or in doubt) nature of the identity history. Dr. Maas selected the holotype as Plowman & Davis 5054 which was collected in 1974 just across the river from the Pantiacolla site where I first saw this new species in the wild.

The species is characterized by its large, dark green leaves with dark purple undersides and dense covering of white hairs. The bracts are usually appendaged, but appendages are sometimes very small or completely absent. The plants are compact, usually growing to no more than about a meter and a half tall with large leaves closely spaced and pointing upwards rather than horizontal or drooping.

A partial phylogeny was completed by Eugenio Valderrama and his associates in the Chelsea Specht Lab at Cornell University and was published in the journal Frontiers in Plant Science in September 2022. The molecular phylogeny includes samples from my collection in Pantiacolla as well as my collection in Huanuco near Tingo Maria. This new species is in a completely separate clade from 'El Whiskey' or C. acreanus, in a lineage that includes C. sinningiiflorus, C. amazonicus and (strangely) C. rubineus.

HORTICULTURAL NOTES:
This new species is in cultivation in several botanical gardens, from the original Plowman collection from Tingo Maria Botanical Garden in Peru. I have found this to be somewhat difficult to grow and I have lost several of my own accessions of this species.

ACCESSIONS:Click links (if any) to see details of individual collections. R2261- R3265- R3322- R3383- R3548- R3567-


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Photos (if available) of Taxon ID 7830
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Costus obscurus type specimen - Click to see full sized image
Photo# 507 Accession# R0
Costus obscurus type specimen


Costus obscurus type specimen - Click to see full sized image
Photo# 508 Accession# R0
Costus obscurus type specimen


Costus obscurus type specimen - Click to see full sized image
Photo# 509 Accession# R0
Costus obscurus type specimen


Costus obscurus, photo from Skinner R3322 upper and lower leaves - Click to see full sized image
Photo# 266 Accession# R3322
Costus obscurus, photo from Skinner R3322 upper and lower leaves


Costus obscurus, photo from Skinner R3322, Pantiacolla Peru - Click to see full sized image
Photo# 267 Accession# R3322
Costus obscurus, photo from Skinner R3322, Pantiacolla Peru


Costus obscurus, photo from Skinner R3322, Pantiacolla Peru - Click to see full sized image
Photo# 268 Accession# R3322
Costus obscurus, photo from Skinner R3322, Pantiacolla Peru