Federally Listed as Endangered
IUCN Red List Ranking – Critically Endangered (CR C2a, D)
Hawai‘i Natural Heritage Ranking ‐ Critically Imperiled (G1)
Endemism – Kaua‘i, Maui
Critical Habitat ‐ Designated
SPECIES INFORMATION: Melicope knudsenii grows into a tree 3‐10 m tall. This species
is a member of the citrus family (Rutaceae). Inflorescences are often large, with up to 200
flowers. The tree has smooth grey bark and yellowish brown to olive‐brown hairs on the
tips of the branches. Leaves are variable, ranging from oblong to elliptic, 3.5 to 9.8 inches
long and 1.8 to 3.9 inches wide. The lower surface of the leaves is uniformly covered
with olive‐brown hairs. The densely hairy flowers are bisexual or may be unisexual.
Flower clusters usually contain 20‐200 flowers per cluster. The sepals and petals are
covered with silky grey hairs and the sepals persist in fruit.
: Kaua‘i, in Olokele Valley and Waimea Canyon; East Maui at Auwahi.
: On Kaua‘i fewer than 5 plants are known. On Maui, the last wild trees
have now died.
LOCATION AND CONDITION OF KEY HABITAT
: Acacia koa‐Metrosideros
Montane Mesic Forest. On Maui this species is found
within Haleakalā National Park. On Kaua‘i it is found on State land in the Koaie
drainage area of Waimea Canyon. M. knudsenii’s habitat is subject to degradation by
feral ungulates and introduction of invasive alien plant species. Associated native
species include Syzygium sandwicensis, Cheirodendron trigynum, Myrsine lessertiana, Ilex
anomala, Alphitonia ponderosa, Zanthoxylum dipetalum, Kadua terminalis, Pleomele aurea,
Bobea, Tetraplasandra waimeae, Xylosma hawaiiensis, Eurya sandwicensis, Psychotria
mariniana, Melicope anisata, Melicope barbigera, Pouteria sandwicensis, Dodonaea viscosa, and
Alien plants, including Erigeron karvinskianus, Triumfetta semitriloba, and Grevillea
Forest & Kim Starr, HEAR
Feral ungulates (pigs, goats, cattle);
On Maui, the speciesʹ habitat has been converted to pasture and has been
steadily degraded by grazing.
: The goals of conservation actions are not only to protect
current populations, but also to establish new populations to reduce the risk of
extinction. In addition to common statewide and island conservation actions, specific
Survey historical range for surviving populations;
Establish secure ex‐situ stocks with complete representation of remaining
Augment wild population and establish new populations in safe harbors.
Continue surveys of population and distribution in known and likely habitats;
Monitor plants for insect damage and plant diseases.
Develop proper horticultural protocols and pest management;
Survey ex‐situ holdings and conduct molecular fingerprinting;
Conduct pollination biology and seed dispersal studies;
Map genetic diversity in the surviving populations to guide future re‐
introduction and augmentation efforts.
International Union for Conservation of Nature and Natural Resources, 2004, IUCN Red List of
Threatened Species: Data Base Search, http://www.redlist.org/search/search‐basic.html.
Hawai‘i Natural Heritage Program, 2005. Hawaii Natural Heritage Program Search,
Starr, Forest, and Kim Starr. 2005. HEAR, Plants of Hawaii website.
www.hear.org/starr/hiplants/images/600max/htm... [August, 2005].
Wagner, W.L., Herbst, D.R., and Sohmer, S.H., 1999. Manual of the Flowering Plants of Hawaiʹi‐‐
Revised Edition. Honolulu, HI: University of Hawaii Press and Bishop Museum Press. 1853p.
Wagner, W. L., D. R. Herbst, and D. H. Lorence. 2005‐. Flora of the Hawaiian Islands website.
http://ravenel.si.edu/botany/pacificislandbiodiversity/hawaiianflora/index.htm [August, 2005].