Ma'o Hau Hele

Hibiscus brackenridgei

Description

Hibiscus brackenridgei (ma'o hau hele), a member of the mallow family and Hawaii's state flower, is a sprawling to erect shrub or small tree that grows up to 16 ft (4.9 m) tall. Young branches, leaves, and some flower parts vary in the degree of hairiness. The leaves—about 2-6 in (5.1-15.2 cm) in both length and width—have three to seven lobes and are generally heart shaped in outline. Beneath each leaf stalk is a pair of very thin stipules (leaflike appendages), 0.2-0.6 in (5.1-15.2 mm) long, that fall off early in development, leaving an elliptic scar. Flowers are borne singly or in small clusters. The petals, which are 1.4-3.1 in (3.6-7.9 cm) long, are yellow, and there is often a maroon spot in the center of the flower. Each triangular calyx lobe is reddish to yellow and usually has a raised, elongated gland on the midrib. Seven to 10 bracts are attached below the calyx. The staminal column, which has anthers attached to the upper three-fourths or nearly to the base, extends beyond the petals. The fruits are somewhat round or oval capsules, 0.4-0.8 in (1-2 cm) long, with a beaklike appendage at one end. This species differs from other members of the genus in having yellow petals, a distinctive calyx, seven to ten bracts attached below the calyx, and thin stipules that leave scars behind after they fall off.

Asa Gray described H. brackenridgei in 1838 from a specimen collected on West Maui. Then, in 1930, Edward Leonard Caum published the varieties molokaiana and kauaiana from type specimens collected in the islands of Molokai and Kauai. The additional variety mokuleiana was named by Sister Margaret James Roe in 1961. David Bates recognized the subspecific designations ssp. mokuleianus and ssp. brackenridgei (including var. molokaiana ) in 1990. He placed H. brackenridgei var. kauaiana in synonymy with a non-Hawaiian species of hibiscus, H. calyphyllus.

H. brackenridgei is known to flower continuously from early February through late May. It flowers intermittently at other times of the year, a condition that may possibly be tied to day length.

Habitat

H. brackenridgei occurs in lowland dry to mesic forest and shrubland from 425-2,625 ft (130-800 m) in elevation. Associated plant species include 'a'ali'i, alahe'e, Erythrina sandwicensis (wiliwili), Reynoldsia sandwicensis ('ohe), and Sida fallax ('ilima).

Distribution

The two recognized subspecies of H. brackenridgei each had a different historical range. H. brackenridgei ssp. brackenridgei was known historically from Laau Point on Molokai, from scattered locations on Lanai, and from Pohakea Gulch south to near McGregor Point on West Maui. H. brackenridgei ssp. mokuleianus was known historically on Oahu from scattered locations in the Waianae Mountains.

As of 1997 H. brackenridgei was known from Oahu, Lanai, Maui, and Hawaii; it may possibly occur on Kauai. The 11 extant populations harbored approximately 311-361 individuals. One population was planted at Kanepuu Preserve and appears to be reproducing naturally.

Threats

The primary threats to H. brackenridgei are 1) habitat degradation and possible predation by pigs, goats, axis deer, and cattle, 2) competition with alien plant species (koa haole, fountain grass, java plum), 3) road construction, and 4) reduced reproductive vigor or stochastic extinction due to the small number of existing populations and individuals.

H. brackenridgei, the official state flower of Hawaii, is a very attractive member of a genus known for its immense horticultural popularity. Unrestricted collection for horticultural or scientific purposes could become a potential threat due to the small numbers of this species.

Conservation and Recovery

The State Division of Forestry and Wildlife has fenced some of the known populations of this species. In addition, approximately 25 propagated plants of H. brackenridgei ssp. brackenridgei were out-planted in the Puuwaawaa/Kaupulehu area before 1993. Some of these plants were burned during the Kaupulehu fire of 1993 but have resprouted from their bases and appear to be thriving.

Two propagated plants of H. brackenridgei ssp. mokuleianus were outplanted in 1994 by the Nature Conservancy of Hawaii in Honouliuli Preserve in fenced enclosures for protection from hoofed mammals. Weeds, slugs, and rodents are also controlled. Both plants have survived and at least one has flowered.

A fuel reduction treatment was implemented at Kanepuu Preserve during 1997-98, and a fire protection plan was developed for the preserve. It is expected that these actions will enhance conservation of the H. brackenridgei ssp. brackenridgei plants found there.

More than 900 seeds are in storage at the National Tropical Botanical Gardens. While seed germination tests indicate a germination rate of 30% for fresh seeds, no germination of seeds occurred after 45 days in storage.

Contacts

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

Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-1201
Fax: (808) 541-1216

Reference

U.S. Fish and Wildlife Service. 10 November 1994. "Endangered Status for 12 Plants from the Hawaiian Islands." Federal Register 59 (217): 56333-56351.