Hau Kuahiwi (Hibiscadelphus giffardianus)
|Listed||October 10, 1996|
|Description||Tree that grows up to 23 ft (7 m) tall; heart-shaped leaf blades; solitary flowers.|
|Habitat||Montane mesic forest.|
|Threats||Bark, flower, and fruit feeding by roof rats; leaf damage by the two-spotted leafhopper, and yellowing by the native plant bug; competition from the alien grasses; habitat change from volcanic activity.|
Hibiscadelphus giffardianus, of the mallow family (Malvaceae), is a tree up to 23 ft (7 m) tall with the trunk up to 12 in (30.5 cm) in diameter and whitish bark. The leaf blades are heart-shaped and 4-12 in (10.2-30.5 cm) long with a broad tip, a notched base, and stalks nearly as long as the blades. Flowers are typically solitary in the axils of the leaves and have stalks 0.6-1.6 in (1.5-4 cm) long. Five to seven filament-like bracts are borne below each flower and the calyx is pouch-like. The overlapping petals form a curved bisymmetrical flower with the upper petals longer, typical of bird-pollinated flowers. The flowers are grayish green on the outside and dark magenta within, and 2-3 in (5-7.5 cm) long. The fruit is woody with star-shaped hairs. This species differs from others in this endemic Hawaiian genus by its flower color, flower size, and filamentous bracts.
H. giffardianus was named to honor W. M. Giffard, who first saw the taxon in 1911. This species was used as the type specimen to describe Hibiscadelphus as a new genus, meaning "brother of Hibiscus". This taxonomy was retained in the latest treatment of the genus.
This taxon grows in mixed Montane Mesic Forest at elevations between 3,900-4,300 ft (1188.7-1310.6 m). Associated taxa include 'ohi'a, koa, Sapindus saponaria (a'e), ho'i'o, Coprosma sp. (pilo), Pipturus albidus (mamaki), Psychotria sp. (kopiko), Nestegis sandwicensis (olopua), Melicope sp. (alani), Dodonaea viscosa ('a'ali'i), Myoporum sandwicense (naio), and introduced grasses.
Only one tree of H. giffardianus has ever been known in the wild, from Kipuka Puaulu (or Bird Park) in Hawaii Volcanoes National Park. This tree died in 1930, but plants exist in cultivation from seeds originally collected by Giffard before the tree died. Cuttings from these cultivated trees have been planted back into the now fenced original habitat at Kipuka Puaulu and currently nine mature plants and two suckers are known to exist. Individuals planted in Kipuka Ki were later determined to be hybrids and were removed by Park personnel. The cultivated plants in Kipuka Puaulu have spontaneously produced fertile hybrids with cultivated plants of H. hualalaiensis that were also planted into Kipuka Puaulu and Kipuka Ki. Both the H. hualalaiensis and the hybrids have been removed from the Park. H. giffardianus has been listed as endangered in the IUCN Plant Red Data Book.
The major threats to H. giffardianus are bark, flower, and fruit feeding by roof rats; leaf damage in the form of stippling and yellowing by the two-spotted leafhopper, and yellowing by the native plant bug Hyalopeplus pellucidus; competition from the alien grasses meadow ricegrass, Hilo grass, and Dallis grass; 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 existing cultivated individuals, all from a single parent. Cattle were known in the area before it became a National Park and probably had a large influence on the habitat.
Conservation and Recovery
As of May 1998, Hawaii Volcanoes National Park had five plants in their nursery; Volcano Rare Plant Facility had nine; National Tropical Botanical Garden had two. Hawaii Volcanoes National Park fenced the outplanted Kipuka Pauulu population in the 1960s and weed control efforts have recently been undertaken. There had been some effort to trap rodents. The Hawaii Department of Agriculture is reaching for biocontrol agents for the two-spotted leafhopper.
U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
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, OR. 80 pp. + appendices.