|Listed||February 25, 1994|
|Description||Shrub or tree with oval or elliptical leaves, and flaring, dark red-petaled flowers.|
|Habitat||Lowland dry forests.|
|Threats||Alien plants; human impact; low populations.|
Clay's hibiscus (Hibiscus clayi ), a shrub or tree in the mallow family, grows to a height of 13-26 ft (4-8 m) and has stems bearing sparse hairs at the branch tips. The oval or elliptical leaves are usually 1-3 in (2.5-7.5 cm) long and 0.6-1.4 in (1.5-3.5 cm) wide and have a hairless upper surface and slightly hairy lower surface. The leaf margins are entire or toothed toward the apex. The flowers are borne singly near the ends of the branches. The flaring petals are dark red, 1.8-2.4 in (4.5-6 cm) long, and 0.4-0.7 in (1-1.8 cm) wide. The green tubular or urn-shaped calyx is usually 0.6-1 in (1.5-2.5 cm) long with five or six shorter bracts beneath. The fruits are pale brown capsules, 0.5-0.6 in (1.3-1.5 cm) long, containing about 10 oval, brownish-black seeds about 0.16 in (4 mm) long. This species is distinguished from other native Hawaiian members of the genus by the lengths of the calyx, calyx lobes, and capsule and by the margins of the leaves.
Clay's hibiscus is found in lowland dry forests at elevations of 750-1,150 ft (230-350 m). This forest type is characterized by an annual rainfall of 20-80 in (50-200 cm), almost all of which falls in winter, and its terrain is a well-drained, highly weathered substrate rich in aluminum. Associated vegetation include Java plum, koa, kukui, and ti.
Clay's hibiscus, known from only scattered locations on private and state land on the Hawaiian island of Kauai, occurs in the Kokee region of the western side of the island, Moloaa Valley to the north, Nounou Mountain in Wailua to the east, and as far south as Haiku near Halii stream. It is unclear whether the one tree at the Kokee location was a cultivated plant.
The only population known to exist in the Nounou Mountains is comprised of four trees.
Cattle greatly damaged the habitat of Clay's hibiscus before they were removed from the area. Competition with alien plants threatens this species. Strawberry guava is the greatest threat, but common guava, Hilo grass, Java plum, kukui, lantana, ti, and Christmas berry are also present in numbers great enough to be current or potential threats. The area of the Nounou Mountain population has been planted with columnar araucaria, which is reseeding itself and may prevent regeneration of native plants. The close proximity of most of the plants to a hiking trail makes them prone to disturbance. Pigs pose a potential threat to the species. The small total number of existing individuals poses a threat of stochastic extinction and reduced reproductive vigor.
Conservation and Recovery
Clay's hibiscus has been successfully propagated and then cultivated by Lyon Arboretum, the National Tropical Botanical Garden (NTBG), and Waimea Arboretum. Present holdings at Lyon Arboretum consist of two plants in the nursery and 22 plants on Lyon Arboretum grounds. The NTBG has seeds in storage as well as plants growing in their garden, and Waimea Arboretum had 21 plants and 100 seedlings in 1995.
The Kauai District of the State of Hawaii's Division of Forestry and Wildlife has outplanted 11 Clay's hibiscus in the Kalepa and Nounou Forest Reserves.
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
Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-1201
Fax: (808) 541-1216
U. S. Fish and Wildlife Service. 25 February 1994. "Determination of Endangered or Threatened Status for 24 Plants from the Island of Kauai, HI." Federal Register 59 (38): 9304-9329.