Hau Kuahiwi

Hibiscadelphus hualalaiensis

Description

Hibiscadelphus hualalaiensis, also called Hau Kuahiwi, of the mallow family, is a tree 16-23 ft (4.8-7 m) tall with the trunk 12 in (30.5 cm) in diameter and whitish bark. The leaf blades are heart-shaped and 4-6 in (10.2-15.3 cm) long with a broad tip, a notched base, stellate hairs, and stalks 1.5 to 4 in (3.8-10.2 cm) long. One or two flowers are borne in the axils of the leaves and have stalks 0.6-5.5 in (1.5-14 cm) long. Five toothlike bracts are borne below each flower and the calyx is tubular or pouch-like. The overlapping petals form a curved bisymmetrical flower with longer upper petals, typical of bird-pollinated flowers. The flowers are greenish yellow on the outside and yellowish green, fading to purplish within, and 0.8-2.2 in (2-5.6 cm) long. The fruit is woody and the seeds have a dense covering of hairs. The species differs from others in this endemic Hawaiian genus by its flower color, smaller flower size, and toothlike bracts.

H. hualalaiensis was named after Hualalai, the volcano on which the plant was found in 1909. This taxonomy was retained in the latest treatment of the genus.

Habitat

This species grows in mixed dry to mesic forest remnants on lava fields, at elevations between 3,000 and 3,350 ft (914.4 and 1,021 m). Associated taxa include 'ohi'a, lama, Sophora chrysophylla (mamane), naio, Pouteria sandwicensis ('ala'a), Charpentiera sp. (papala), Nothocestrum sp. ('aiea), Claoxylon sandwicense (po'ola), and kikuyu grass.

Distribution

H. hualalaiensis was historically known from three populations, located in the Puu Waawaa region of Hualalai, on the island of Hawaii. The last known wild tree was in Puu Waawaa I Plant Sanctuary, owned and managed by the Department of Land and Natural Resources, State of Hawaii. This tree died in 1992, but 12 cultivated trees have been planted within the fenced sanctuary. In addition, approximately ten cultivated plants can be found near the State's Kokia Sanctuary in Kaupulehu. Cultivated individuals were planted in Kipuka Puaulu in Hawaii Volcanoes National Park, but were removed to prevent further hybridization with the H. giffardianus plants that are native to the kipuka. The area where the plants are presently found is surrounded by State land that is leased for cattle ranching.

Threats

The major threats to H. hualalaiensis are fire; cattle, pigs, and sheep that may get through the fence; flower and seed feeding by roof rats; competition from alien plants such as kikuyu grass and lantana; ranching activities; habitat change from volcanic activity; and a risk of extinction from naturally occurring events and/or reduced reproductive vigor due to the small number of known cultivated individuals from a single parent.

Conservation and Recovery

Twelve trees cultivated by Division of Forestry and Wildlife were planted on state land within one fenced enclosure in Puu Waawaa Wildlife Sanctuary and as of 1996 ten survived. As additional five plants were outplanted in this enclosure in November 1997. Another five plants were outplanted in another enclosure with Puu Waawaa. In addition, some ten plants were cultivated and out-planted by Division of Forestry and Wildlife near Koaia Sanctuary in Kawaihae. Cultivated individuals were planted in Kipuka Puaulu in Hawaii Volcanoes National Park but were removed to prevent further hybridization with the H. giffardianus plants that are native to the kipuka. Volcano Rare Plant Facility holds ten plants in their nursery. National Tropical Botanical Garden has 19 plants from three accessions, along with 228 seeds in storage. Waimea Falls Park has four plants but they are doing poorly. Small areas have been fenced around all outplanted populations to exclude livestock and feral animals.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 1998. "Big Island II: Addendum to the Recovery Plan for the Big Island Plant Cluster." U.S. Fish and Wildlife Service, Portland, Oregon. 80 pp. + appendices.