A member of the Ginseng family (Araliaceae), Polyscias racemosa, formerly known as Munroidendron racemosum, is a 7 m (~ 23 ft) tall tree with a straight trunk and spreading branches. It has smooth, gray bark. Leaves are 15 to 30 centimeters (~ 6-12 in) long, and are made up of many oval leaflets, each of which are 8 to 17 centimeters (~ 3-7 in) long. These trees drop most of their leaves during their summer blooming season. The small, pale yellow flowers hang in long, loose bunches. (Wagner,W.L.,Herbst,D.R.,Sohmer,S.H. 1990. Manual of Flowering Plants of Hawai'i.)
Threats to Polyscias racemosa include competition with alien plant species, such as Aleurites moluccana (Kukui), Psidium guajava (Guava), Lantana camara (Lantana), and Leucaena leucocephala (Koa Haole). Other threats include habitat degradation by feral goats, fire, and fruit predation by rats. In addition, a mature, cultivated tree was observed being killed by an introduced insect of the long-horned beetle family (Cerambycidae).This beetle could potentially attack and damage or kill wild trees (USFWS.2000.) The National Tropical Botanical Garden (NTBG) currently has ex situ holdings in its seed bank, which represents two out of the fifteen populations. In addition, there are approximately 400 plants growing in the nursery. The Kaua'i District, Department of Land and Natural Resource, and the Department of Forestry and Wildlife outplanted approximately 400 individuals at Kauhao Ridge, and additional outplanting is planned. Other outplanting sites include: Sleeping Giant, DLNR Kalalau Exclosure, and Ha'upu. The Lyon Arboretum, NTBG, and the Waimea Arboretum have successfully propagated Polyscias racemosa. (USFWS.1995.) Research Management Needs: 1. Fence and manage surviving wild populations of P. racemosa. 2. Test the influence of weeding and fencing on populations of P. racemosa. 3. Conduct pollination biology genetics and seed dispersal studies. Ex Situ Needs: 1. Establish secure ex situ stocks with full founder representation. 2. Develop proper horticultural protocols and pest management for P. racemosa. 3. Survey ex situ holdings and conduct molecular fingerprinting of P. racemosa. (Recommendations derived from Chapin,M.H. and Maunder,M.)
Polyscias racemosa is used as a landscape species and will reach twenty to twenty-five feet in height. This small tree has a strong, slender trunk and attractive flowers and foliage. It is unusual in appearance and works well as a specimen tree or for a background planting.
Polyscias racemosa is an extremely rare endangered endemic plant from Kaua'i. It grows in moist forests from 390 to 1,300 feet. It occurs naturally in only 3 locations on Kaua'i: Nounou Mountain, Na Pali cliffs, and Ha'upu Ridge near Nawiliwili Bay and Waimea Canyon. (Wagner,W.L.,Herbst,D.R.,Sohmer,S.H. 1990. Manual of Flowering Plants of Hawai'i.)
Polyscias racemosa is a hermaphrodite and is believed to be insect-pollinated. Its seeds are presumed to be bird dispersed. (Sakai et al.1995.) Because each population of this species contains only a small number of trees, the species is threatened by extinction from naturally occurring events, such as landslides or hurricanes.(USFWS.2000.)
Formerly considered to belong to the genus Munroidendron, it was named in honor of George Campbell Munro (1866-1963), with the suffix "dendron" (tree) added. Noted as an early conservationist and botanical explorer, especially on Lanai, Munro was manager of Molokai Ranch early in 20th century and was one of the first to find this plant. He was particularly famed as an ornithologist and was the author, in 1944, of the popular and beautifully illustrated Birds of Hawaii. (Green,P.S. 1996. A Hawaiian Florilegium.)
Polyscias racemosa is an extremely rare, endangered and endemic species.
There is no record of specific uses for Polyscias racemosa, but there is for P. sandwicensis where the wood was used for stilts in a game called Kukuluae'o (Gon 2008.)
The National Tropical Botanical Garden (NTBG) and the University of Hawaii are working on a study on Polyscias racemosa population genetics. (Maunder.M, pers.comm. 2002.) The National Seed Storage Laboratory (NSSL) found inconclusive results after testing the seeds of Polyscias racemosa. The seeds are probably not tolerant to freezing. The laboratory germination time was 6 months. (Yoshinaga. 2002.)
