Tropical Plant Database - Plant Details

Hibiscadelphus distans is a shrub or small tree that grows up to 5 meters tall. The leaves are heart-shaped, typically 4-10 cm in length, with irregular (rounded) serations on the margins. 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.)

Currently H. distans populations are managed by the Hawaiian Division of Forestry and Wildlife (DOFAW). 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 is found only on the island of Kaua'i, Hawai`i. This species is found in a single natural population above Koai'e Stream in Waimea Canyon in a small remnant patch of open, dry forest at approximately 350 m in elevation. 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.)

The Hawaiian name Hau kuahiwi can be literally translated as "upland Hau" in reference to the common lowland species Hau (Hibiscus tiliaceus) which is also in the Malvaceae (Mallow) family. 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)

Kauai Hau Kuahiwi is endemic to Kaua'i meaning this is the only location in the world where this species is found. 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)

Seeds of Hibiscadelphus distans have been tested by the National Seed Storage Laboratory (NSSL) and the National Tropical Botanical Garden (NTBG) to determine their viability following a range of preservation treatments. 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.)

We currently have 30 herbarium specimens for Hibiscadelphus distans in our collection. Click on any specimen below to view the herbarium sheet data.

• S047696 - collected by Steve Perlman in Unknown
• 044616 - collected by Tim Flynn in 1982
• 044617 - collected by Tim Flynn in 1983
• 014938 - collected by Steve Perlman in 1987
• 014941 - collected by Steve Perlman in 1987
• 010771 - collected by Chipper Wichman in 1990
• Unassigned - collected by K. R. Wood in 1991
• Unassigned - collected by K. R. Wood in 1991
• 040336 - collected by K. R. Wood in 1991
• 015940 - collected by K. R. Wood in 1991
• 015939 - collected by K. R. Wood in 1991
• 027380 - collected by Tim Flynn in 1992
• 013823 - collected by K. R. Wood in 1992
• 018038 - collected by Larry Rueter in 1994
• 025345 - collected by David H. Lorence in 1997
• 045772 - collected by Steve Perlman in 2004
• 045765 - collected by Steve Perlman in 2004
• Unassigned - collected by Steve Perlman in 2005
• Unassigned - collected by Steve Perlman in 2005
• 063068 - collected by Nicole Shores in 2012
• 085362 - collected by David H. Lorence in 2015
• S068946 - collected by David H. Lorence in 2015
• 071484 - collected by Susan M. Deans in 2016
• 075774 - collected by Dustin Wolkis in 2016
• 081207 - collected by Seana Walsh in 2018
• Unassigned - collected by Ben Nyberg in 2021
• Unassigned - collected by Ben Nyberg in 2021
• Unassigned - collected by Ben Nyberg in 2021
• Unassigned - collected by Ben Nyberg in 2021
• Unassigned - collected by Ben Nyberg in 2021