CPC Plant Profile: Mann's Bluegrass
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Plant Profile

Mann's Bluegrass (Poa mannii)

Closeup of tufted culms with erect habit. Photo Credit: D. Lorence
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Poaceae
  • State: HI
  • Nature Serve ID: 148394
  • Date Inducted in National Collection: 07/09/1992

There are three endangered Poa species endemic to Hawaii (U.S. Fish and Wildlife Service [USFWS] 2001), and all are found only on the island of Kauai. P. mannii, a member of the grass family (Poaceae) is a perennial grass with short rhizomes (underground stems) and erect, tufted culms (hollow or pithy stalks or stems). P. mannii is distinguished from both P. siphonoglossa and P. sandvicensis by its fringed (with hair or bristles along margins) ligules and from P. sandvicensis by its shorter panicle branches. (USFWS 1995) Little is known about the life history of P. mannii. Flowering cycles, pollination vectors, seed dispersal agents, longevity, specific environmental requirements, and limiting factors are unknown.

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Center for Plant Conservation
  • 08/19/2021
  • Orthodox Seed Banking

In 2021, CPC contracted National Tropical Botanical Garden to recollect seed from a population currently held in long term orthodox seed storage as part of an IMLS-funded seed longevity experiment. The National Laboratory for Genetic Resources Preservation will evaluate how germination tested viability and RNA Integrity of seed lots decline over time in storage.

Nature Serve Biotics
  • 05/02/2017

Endemic to the island of Kauai. It is currently known from about 7 occurrences, with fewer than 200 plants. The species and its habitats are threatened by feral goats and pigs, and alien plant species.

  • 01/01/2010

Threats to P. mannii include habitat damage, trampling, and browsing by feral goats, and competition with invasive alien plants. Erigeron karvinskianus (daisy fleabane) has invaded Kalalau, Koaie, and Waialae Valleys, three of the areas where P. mannii oc

  • 01/01/2010

Number of Populations: 7 (USFWS 2001) Number of Plants: 135 (USFWS 2001)

  • 01/01/2010

The National Seed Laboratory (NSSL) tested the seeds of P. mannii, finding that they are not recalcitrant and can tolerate freezing (Yoshinaga 2002).

  • 01/01/2010

A critical habitat designation has been proposed for P. mannii (USFWS 2002). The National Tropical Botanical Garden (NTBG) currently has ex situ holdings of seeds in its seed bank, which represents two out of the seven populations. In addition, there are three plants that represent an additional population growing in the grounds of the botanical garden.

  • 01/01/2010

1. Secure all wild populations through sight management. 2. Conduct pollination biology studies. 3. Test the influence of weeding and fencing on populations of P. mannii. 4. Map genetic diversity in the surviving populations of P. mannii. Recommendations derived from M.H. Chapin, M. Maunder, and USFWS (1995).

  • 01/01/2010

1. Establish secure ex situ stocks with full founder representation. 2. Develop proper horticultural protocols and pest management for P. mannii. 3. Survey ex situ holdings and conduct molecular fingerprinting. Recommendations derived from M.H. Chapin and M. Maunder.


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Taxon Poa mannii
Authority Munro ex Hillebr.
Family Poaceae
CPC Number 3538
ITIS 41167
Common Names Manns bluegrass | Mann's blue grass | Olokele Gulch bluegrass
Associated Scientific Names Poa mannii
Distribution P. mannii is endemic to Kauai and was historically found in Olokele Gulch. Today, they can be located in Kalalau Valley, Makaha Valley, Koaie Valley, and Waialae Valley (USFWS 2000).
State Rank
State State Rank
Hawaii S1

P. mannii typically grows on cliffs, rock faces, or stream banks in lowland or montane wet, mesic. P. mannii can also be found in dry Metrosideros polymorpha (ohia) forests or Acacia koa (koa)-M. polymorpha montane mesic forest. They grow at elevations between 460 and 1,150 meters (1,510 and 3,770 ft). Associated species of P. mannii include Chamaesyce celastroides var. hanapepensis (akoko), Artemisia australis (ahinahina), Bidens sandwicensis (kookoolau), Lobelia sandwicensis (no common name [NCN]), Wilkesia gymnoxiphium (iliau), Eragrostis variabilis (emoloa), Panicum lineale (NCN), Mariscus phloides (NCN), Luzula hawaiiensis (NCN), Carex meyenii (NCN), C. wahuensis (NCN), Cyrtandra wawrae (haiwale), Exocarpos luteolus (heau), Labordia helleri (kamakahala), Nototrichium sp. (kului), Hedyotis terminalis (manono), Melicope anisata (mokihana), M. barbigera (pelea), M. pallida (alani), Pouteria sandwicensis (alaa), Schiedea membranacea (NCN), Diospyros sandwicensis (lama), Psychotria mariniana (kopiko), P. greenwelliae (Kauai wild coffee), Kokia kauaiensis (kokio), Alectryon macrococcus (Hawaii macrocossus), Antidesma platyphyllum (hame), Bidens cosmoides (poola ni), Dodonaea viscosa (aalii), and Schiedea amplexicaulis (NCN).

Ecological Relationships

The breeding system of P. mannii is unknown. This species is wind-pollinated and their seeds are bird dispersed (Sakai et al. 1995).

Common Name Name in Text Association Type Source InteractionID
Lead Institution State Reintroduction Type Year of First Outplanting

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