|Listed||October 10, 1996|
|Description||Perennial bunchgrass with loosely branched inflorescences that are 6-14 in (15.2-35.6 cm) long.|
|Habitat||Scattered in sand dunes in a coastal shrubland.|
|Threats||Off-road vehicles; competition with alien plant species.|
Panicum niihauense is a perennial bunchgrass with unbranched culms 20-49 in (51.0-124.5 cm) in length. The flat leaf blades are 6-14 in (15.2-35.6 cm) long and 0.3-0.7 in (0.8-1.8 cm) wide. The panicles (loosely branched inflorescences) are 5-14 in (12.7-35.6 cm) long. The panicle branches lie close to the main stem of the inflorescence (not spreading outward), and the spikelets are borne densely along the inflorescence branches. The spikelets that contain two flowers are 0.1 in (0.25 cm) long. This species is distinguished from others in the genus by its erect and appressed inflorescence branches, as well as by its densely clustered arrangement of spikelets.
J. F. Stokes collected a grass on Niihau in 1912 that Harold St. John later named P. niihauense. This species has been maintained in the most recent treatment of Hawaiian members of the genus.
P. niihauense is found scattered in sand dunes in a coastal shrubland at 30-50 ft (9-15 m) elevation. Associated plant species include 'a'ali'i, Cassytha filiformis (kaunaoa pehu), Prosopis pallida (kiawe), Scaevola sericea (naupaka), Sida fallax ('ilima), and Vitex sp. (kolokolo kahakai).
P. niihauense was known historically from Niihau where it was last collected in 1949, and one location on Kauai. In 1996, this species was only known from a single population of 23 individuals on state-owned land at Polihale State Park on Kauai.
The primary threats to the only known population of P. niihauense are off-road vehicles, competition with alien plant species, and a risk of extinction from naturally occurring events and reduced reproductive vigor due to the very small number of remaining individuals.
Collecting for scientific or horticultural purposes and visits by individuals avid to see rare plants are potential threats to P. niihauense, of which the remaining population is well-known.
The only known population of P. niihauense on Kauai is threatened by several alien plants, including koa haole and kiawe.
Conservation and Recovery
More than 3,000 seeds were in storage at National Tropical Botanic Gardens in 1997, although the plant has not yet been cultivated there.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
U. S. Fish and Wildlife Service. 10 October 1996. "Determination of Endangered or Threatened Status for Fourteen Plant Taxa from the Hawaiian Islands." Federal Register 61 (198): 53108-53124.