Classification:

Kingdom: Plantae-Plants
Subkingdom: Tracheobionta-Vascular plants
Superdivision: Spermatophyta-Seed plants
Division: Magnoliophyta-Flowering plants
Class: Magnoliopsida-Dicotyledons
Subclass: Dilleniidae
Order: Malvales
Family: Malvaceae - Mallow family
Genus: Hibiscadelphus Rock - Hibiscadelphus
Species: Hibiscadelphus distans Bishop & Herbst - Kauai Hau Kuahiwi

(USDA, NRCS. 2006. The PLANTS Database, 6 March 2006 (http://plants.usda.gov). Data compiled from various sources by Mark W. Skinner. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.)
(Wagner, W. L., Herbst, D. R., and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai`i. Revised Edition. Volume 1. Bishop Museum Special Publication 97. University of Hawai`i Press, Bishop Museum Press, Honolulu, Hawai`i.)

Both upper and lower leaf surfaces have branched stellate (star-shaped) hairs. Unlike most other Hawaiian members of the Mallow (Malvaceae) family which are radially symmetric, the flowers of Hibiscadelphus distans are bilaterally symmetric. The flowers are 3-4 cm long and are subtended by triangular green bracts. The calyx is largely fused to form a tube surrounding the petals which are greenish yellow and turn maroon with age. The fruit of Hau kuahiwi is a woody capsule (2.5 cm long, 1.5 cm wide) that becomes dry when mature and splits open to release the seeds. The capsule is divided into five sections with two seeds in each section that are about 5 mm long and covered with fine yellowish brown hairs.

(Wagner, W. L., Herbst, D. R., and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai`i. Revised Edition. Volume 1. Bishop Museum Special Publication 97. University of Hawai`i Press, Bishop Museum Press, Honolulu, Hawai`i.)

This region receives approximately 150 cm of rain annually and has a yearly mean temperature that ranges from 18.5 to 25.7 oC (65 to 78 oF).

(Wagner, W. L., Herbst, D. R., and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawai`i. Revised Edition. Volume 1. Bishop Museum Special Publication 97. University of Hawai`i Press, Bishop Museum Press, Honolulu, Hawai`i.)

This species is listed as an endangered species by the US Fish and Wildlife Service. The only known populations are in Koai`e canyon in the Pu`u Ka Pele Forest Reserve, Waimea Canyon, Kaua`i and include 106 known individuals. It is estimated that less than 200 individuals persist in the wild.

(US Fish and Wildlife Service. 2005. Threatened and endangered species system. http://ecos.fws.gov/tess_public/. 15 Apr. 2006)
(US Fish and Wildlife Service. 1986. Final Listing, Endangered ETWP; Determination of End. Status for Hibiscadelphus distans (Kauai Hau Kauahiwi); Federal Register, 51 (62), 51 FR 15903 15906)

Four exclosures have been erected around naturally occurring plants to protect them from human disturbance and ungulate grazing pressure. Propagation of seedlings from seed collections has facilitated the outplanting of seedlings into exclosure sites. Regeneration within these populations is being monitored and in two exclosures natural regeneration has been observed. This species is in cultivation at the McBryde Garden of the National Tropical Botanical Garden.

Multiple threats have been identified to the persistence of H. distans populations in their native habitat. These include competition from introduced plants (e.g. Lantana (Lantana camara)), damage by introduced herbivores (goats) and insects (e.g. pink bollworm (Pectinophora gossypiella)), and human disturbance. As this species if found in a limited number of identified populations these plants are vulnerable to being damaged or extirpated as a result of naturally occurring disturbance including hurricanes, landslides, and fire. The small population size and the limited number of potentially reproductive individuals in these populations means that loss of genetic diversity and inbreeding depression threatens the persistence of these populations. Pollination and seed dispersal mechanisms for Hibiscadelphus distans are currently unknown.

Research Management Needs:
1. Conduct floristic surveys of Waimea Canyon to determine if additional populations exist.
2. Map genetic diversity in the surviving populations.
3. Determine the effect of weeding and fencing on H. distans populations.
4. Conduct pollination biology and seed dispersal studies for H. distans.
5. Secure wild populations through on-site management.

Ex Situ Needs:
1. Establish secure ex situ stocks that represent the maximum genetic diversity of the remaining populations.
2. Develop horticultural and pest management protocols to minimize loss/damage to plants.
3. Survey ex situ holdings and conduct molecular fingerprinting.

US Fish and Wildlife Service. 1986. Final Listing, Endangered ETWP; Determination of End. Status for Hibiscadelphus distans (Kauai Hau Kauahiwi); Federal Register, 51:(62) 51 FR 15903 15906.

Hibiscadelphus distans seeds can tolerate freezing or drying and maintain their viability. Germination in laboratory conditions takes approximately two months.

(Yoshinaga, A. 2002. Seed storage characteristics of Hawaiian species.)

The name hibiscadelphus means "brother of Hibiscus" and alludes to another genera, Hibiscus, which is also in the Malvaceae family.

(Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1990. Manual of the flowering plants of Hawai'i, Bishop Museum Press, Honolulu, Hawai`i)