Tuesday, December 29, 2009

Hibiscus brackenridgei ssp. brackenridgei

Hibiscus brackenridgei  | Ma'o hau hele, Native Yellow Hibiscus, Brackenridge's Rosemallow

Hibiscus brackenridgei is Hawai'i's State flower, and is listed as an endangered species. It was named after William Brackenridge (1810-1893), an American horticulturist and superintendent of the National Botanic Garden in Washington D.C. Hibiscus brackenridgei is native to dry forests and shrub lands at elevations from 120 to 800m (400 to 2,600 ft). It is a shrub that grows up to 3m in height, with maplelike leaves and bright yellow flowers. It is found on all the main Hawaiian islands except Ni'ihau and Kaho'olawe, but it is not common in any location. Hibiscus Brackenridgei is closely related to the Australian Hibiscus divaricatus and some believe that it may not be specifically distinct from it (Wagner, Manual of the flowering plants of Hawaii, 1990).

Hibiscus brackenridgei varies in appearance among islands but generally falls into three subspecies:
      ssp. brackenridgei of Maui, Molokai, Lanai and the Big Island,
      ssp. mokuleianus, The Mokulei Rosemallow of Oahu and Kauai.
      ssp. molokaianus is an extremely rare 3rd subspecies.

The most visible difference between these subspecies is in the leaves and stems. The leaves of ssp. mokuleianus have more serrated margins and pink veins with tiny spines on the branches. Ssp. brackenridgei, on the other hand, has leaves with more rounded margins and yellow veins, and it lacks the tiny spines on its branches.

Historical Reference: Mr. Rock sent in from the island of Oahu (Territory of Hawaii) a showy tree hibiscus (Hibiscus brackenridgei), bearing yellow flowers 6 inches across. From Honolulu, Hawaii. Seed presented by J. F. Rock. Received June 30, 1920. "A striking and well-marked rather rare species with a shrubby erect stem, 4 to 5 feet high, stiff spreading branches, and rather stout, very leafy flowering stalks. It is worthy of cultivation on account of its showy yellow flowers. The smooth, bright-green leaves on long petioles are rounded in outline, 3 to 4 inches in diameter and 5 to 7-lobed, somewhat resembling those of the common grapevine. The spreading yellow corolla is about 6 Inches across. Found In the scrub vegetation of the leeslde of Oahu, East and West Maul, and Lanai."

This extremely rare species of Hibiscus, which Mr. Rock found growing among the stones at the base of a cliff on the windward side of the island of Oahu, is a thing of rare beauty when covered with its large yellow flowers. Since it grows under arid and rather severe conditions it may be found useful as an ornamental plant in some parts of tropical America which, because of unfavorable climate and soil, are not well suited to the cultivation of many of the common tropical ornamentals. The deep canary-yellow flowers of this exceedingly rare Hibiscus are 6 inches across. Only a few wild plants are in existence, and the species seems not to have found its way into American horticulture, although Hillebrand called attention to the possibilities of its culture more than 30 years ago.

   Plant inventory, Issues 61-70
   Agricultural Research Center-West (U.S.). Northeastern Region
   The Dept., 1922