Hawaiian Bluegrass

Poa sandvicensis

Description

Poa sandvicensis (hawaiian bluegrass) is a perennial grass with mostly erect stems that grow 1-3 ft (30-91 cm) high. Short underground stems (rhizomes) form a hard base for the solid, slightly compressed stems. The leaf blades are 4-8 in (10-20 cm) long and up to 0.2 in (.5 cm) wide; the leaf sheaths completely surround the stem. The flowers occur in a complex cluster, and fruits are brown, oval grains. Hawaiian bluegrass is distinguished from similar species by, among other things, its shorter stems, closed leaf sheaths, and longer panicle branches.The species has also been known by the names Festuca sandvicensis and Poa longeradiata.

Habitat

Hawaiian bluegrass is one of a large number of species endemic to the Kokee area in the northwestern part of Kauai. This area is roughly encompassed by the 8 sq mi (21 sq km) Kokee State Park, an area that lies just north of Waimea Canyon, and has the Alakai Swamp to the east, the steep cliffs of the Na Pali coast to the north, and the drier leeward ridges to the west. Hawaiian bluegrass is found on shaded, wet slopes, ridges, and rock ledges in moist to wet mountain forest dominated by ohia at elevations between 3,400-4,100 ft (1,000-1,200 m).

Five other plant species endemic to the Kokee region are listed as Endangered: Chamaesyce hale-manui, Dubautia latifola, Poa siphonoglossa, Stenogyne campanulata, and Xylosma cenatum.

Distribution

Hawaiian bluegrass was first collected in 1864 or 1865 from a location north of Waimea Canyon. Since then it has been found in six areas: the rim of Kalalau Valley in Na Pali Coast State Park, Halemanu and Kumuwela Ridge/Kauaikinana drainage in Kokee State Park, Awaawapuhi Trail in Na Pali-Kona Forest Reserve, Kohua Ridge/Mohihi drainage in the forest reserve and Alakai Wilderness Preserve, and Kaholuamanu on privately owned land.

Hawaiian bluegrass is no longer known from the historic sites of Halemanu in Kokee State Park and the privately owned Kaholuamanu. The four surviving populations of less than 1,000 total individuals, scattered over an area of 10 sq mi (26 sq km) on state-owned land, occur at the Kalalau, Awaawapuhi, Kumuwela/Kauaikinana, and Kohua/Mohihi localities. Hillebrand's questionable reference in 1888 to a Maui locality is most likely an error.

Threats

The major threat to the survival of Hawaiian bluegrass is competition from alien plant species. Daisy fleabane is the primary threat to the Kalalau population. Prickly Florida blackberry threatens three populations, while banana poka, and ginger threaten the Awaawapuhi population.

In addition, feral pigs threaten to degrade native plant habitat in Na Pali-Kona Forest Reserve and Na Pali Coast State Park. Pigs, which have inhabited the forests of Kauai for over a century, have proven extremely destructive to native Hawaiian plant species. Their rooting destroys vegetative cover, allowing the invasion of alien species. Feral pig feces add nutrients to poor soils that would otherwise favor native species.

Various human activities have promoted the spread of feral pigs on Kauai. Past logging and construction of ditch and water diversion systems for agricultural irrigation created a substantial array of pathways for pigs to penetrate into what had been unspoilt habitat. Plum trees planted in the 1930s created a food that attracted the pigs.

In addition to this predictable threat, the low number of existing Hawaiian bluegrass plants and the fact that one population holds 80% of surviving plants puts the species at risk of extinction through unpredictable natural or human events.

Conservation and Recovery

A Recovery Plan for the Hawaiian bluegrass and associated species was published by the Fish and Wildlife Service in 1995. It survives in only four known populations, all on state-owned land managed as natural-area parks and nature reserves. These critical habitats must be rigorously protected from environmental threats. Its habitat must be managed to reduce the damage caused by mammalian herbivores. This could be done by enclosing the plants in secure fencing, or by reducing or eliminating the non-native mammals. The abundance of alien invasive plants must also be reduced in the habitat of the Hawaiian bluegrass. Hiking trails must be located away from its critical habitat. The populations of the Hawaiian bluegrass should be monitored, and research undertaken into its biology and habitat needs, with the aim of developing management practices appropriate to maintaining or enhancing its habitat. The National Tropical Botanical Garden holds Hawaiian bluegrass seeds in storage.

Contacts

U. S. Fish and Wildlife Service
Pacific Islands Ecoregion
300 Ala Moana Boulevard, Room 3-122
P.O. Box 5088
Honolulu, Hawaii 96850.
Telephone: (808) 541-3441
Fax: (808) 541-3470

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
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 1995. "Recovery Plan for the Kauai Plant Cluster." U.S. Fish and Wildlife Service, Portland, OR.