It was discovered in 1991 and described as a new species in 1995. Only four individuals were found at that time; three of those were crushed by a boulder and died between 1995 and 1998, and the last was found dead in 2011. Pollen was found to be inviable, no fruit set was ever observed and all attempts at propagation, including by cross-pollination with H. distans, failed. It was later assessed as extinct by the International Union for Conservation of Nature in 2016, but three individuals were rediscovered in 2019 by the National Tropical Botanical Garden. The plants were growing out of a steep cliff and were found using drones.
Hibiscadelphus woodii inhabits basalt scree and cliff walls in ʻōhiʻa lehua (Metrosideros polymorpha) dominated mixed mesic forests at an elevation of 915 m (3,002 ft). Associated plants include koʻokoʻolau (Bidens sandvicensis), ʻāhinahina (Artemisia australis), alani (Melicope pallida), naʻenaʻe (Dubautia spp.), ʻānaunau (Lepidium serra), nehe (Lipochaeta spp.), kolokolo kuahiwi (Lysimachia glutinosa), Carex meyenii, ʻakoko (Euphorbia spp.), manono (Hedyotis spp.), kuluʻī (Nototrichium spp.), Panicum lineale, kōlea (Myrsine spp.), Stenogyne campanulata, Lobelia niihauensis, and Mann's Bluegrass (Poa mannii).
- "Hibiscadelphus woodii". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 14 May 2015.
- Wood, K.R. (2012). "Possible extinctions, rediscoveries, and new plant records within the Hawaiian Islands" (PDF). Bishop Museum Occasional Papers. Bishop Museum Press. 113: 91–102.
- Clark, M. (2016). "Hibiscadelphus woodii". IUCN Red List of Threatened Species. IUCN. 2016: e.T35153A83801779. doi:10.2305/IUCN.UK.2016-2.RLTS.T35153A83801779.en. Retrieved 13 April 2017.
- Lee, Diane S. W. (19 April 2019). "Kauai researchers rediscover native Hawaiian flower once thought extinct". Honolulu Star-Advertiser. Retrieved 21 April 2019.
- "NTBG Researchers Rediscover 'Extinct' Native Plant Using a Drone". National Tropical Botanical Garden. 16 April 2019. Retrieved 17 April 2019.
- "Hibiscadelphus woodii". CPC National Collection Plant Profiles. Center for Plant Conservation. 22 July 2008. Archived from the original on 30 October 2010. Retrieved 14 November 2009.
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