The single white flowers are pinwheel shaped, up to 4 inches across, and borne at the ends of the branches. The staminal column is pink to red (except in subspecies immaculatus which has a white column). The flowers may be slightly pink or may age to pale pink, and are slightly fragrant. In cultivation, Hibiscus arnottianus blooms almost continuously.

Three subspecies are recognized. Subspecies arnottianus from O'ahu has smooth leaves 1 1/2 to 4 inches long. Subspecies immaculatus is native to Moloka'i and has a white staminal column and leaves with rounded teeth. Subspecies punaluuensis is also native to O'ahu. It is robust with leaves 4 to 10 inches long. (Criley 1998; Criley 1999; Koob 1998; Rauch 1997; Wagner 1990)

Hibiscus arnottianus is easy to grow from fresh seed, but it hybridizes easily and the seedlings may differ from the parent plant. To ensure that the seedlings are not hybrids, hand pollinate the flowers. Using a paint brush, transfer pollen to the stigma of the flower and then enclose the flower in a bag until the seed capsule ripens. Bornhorst recommends hand pollination in the early morning. Pick the capsules just as they turn tan and before they open up. Place them in a container such as a paper bag to dry. As the capsule dries, the seeds will fall out or they can be removed manually.

Soak the seeds in water overnight and plant the ones that sink. Woolliams recommends using warm water. Use a well-drained sterile potting mix such as 2 parts potting soil and 1 part perlite and keep the mix moist. The NTBG plant information sheet suggests putting the seeds in the shade. Koob writes that the seeds generally sprout in 2 to 3 weeks. NTBG says that germination generally occurs in 3 to 9 days. (Bornhorst 1991; Koob 1998; NTBG 1992a; NTBG 1992b; Woolliams 1976)

Reduce transpiration by removing half of each leaf above the rooting medium and use a medium strength rooting hormone. Koob suggests 0.1% indolebutyric acid (IBA) and 0.05% naphthaleneacetic acid (NAA) (Koob, email). Bornhorst (1996) recommends Rootone F or Hormex #3; Bornhorst (1991) also reports the use of a 1:10 Dip N Gro solution. Criley reports success with rooting hormones having a 2 to 1 ratio of IBA to NAA. In this work, good rooting was obtained with total auxin concentrations ranging from 4,000 parts per million (ppm) to 7,500 ppm.

Use a well-drained medium. Bornhorst (1991) reports success with a mixture of 1 part perlite to 1 part vermiculite. Koob suggests clean sand, perlite, or vermiculite; Criley uses either 1 part coarse perlite to 1 part vermiculite or 100% vermiculite; NTBG recommends a mixture of 1 part potting soil and 1 part perlite.

Keep the cuttings in a humid environment and the rooting medium moist. Put the cuttings under a mist system if possible, but a humidity chamber or hand misting twice a day may be adequate. Bornhorst (1991) reports the successful use of a mist system which was one for 24 seconds every 3 minutes. Criley's work was done using an intermittent mist system which was on for 6 to 8 seconds every 5 or 6 minutes; cuttings were rooted under 30% shade. Cuttings are ready to transplant in 2 to 5 months. (Bornhorst 1991; Bornhorst 1996; Criley 1999; Criley 1998; Koob 1998; NTBG 1992a; NTBG 1992b)

To start a plant by air layering, remove the bark and cambium from a 1 inch wide ring of bark. Apply a rooting hormone to the cut surface and cover this with a layer of damp sphagnum moss. Wrap the moss in plastic being sure to secure the ends where it wraps around the branch.

The air layer should be ready to remove from the parent plant in 3 to 5 months. Bornhorst (1996) suggests that root systems from air-layered plants are not as vigorous as those produced by other techniques. (Bornhorst 1991; Bornhorst 1996; Koob 1998)

Bornhorst, Heidi L. 1996. Growing native Hawaiian plants: a how-to guide for the gardener. Honolulu: The Bess Press. p. 35-36.

Bornhorst, Heidi L., and Fred D. Rauch. 1994. Native Hawaiian plants for landscaping, conservation, and reforestation, Research extension series 142. Honolulu: Hawaii Institute of Tropical Agriculture and Human Resources. p. 8-9.

Criley, Richard A. 1998. Propagation of indigenous and endemic ornamental Hawaiian plants. Combined Proceedings of the International Plant Propagators' Society 48:669-674.

Criley, Richard A. 1999. Aloha Hawai'i. American Nurseryman 190 (3):50-61.

Koob, Gregory A. 1998. Koki'o ke'oke'o: a native white hibiscus. Hawai'i Horticulture 1 (12):3-6.

Koob, Gregory A. "Rooting Hormone Question." Personal email. Posted 28 January 1999.

National Tropical Botanical Garden (NTBG). 1992a. Koki'o ke'oke'o [Hibiscus arnottianus]. In Native Hawaiian plant information sheets. Lawai, Kauai: Hawaii Plant Conservation Center. National Tropical Botanical Garden. Unpublished internal papers.

National Tropical Botanical Garden (NTBG). 1992b. Koki'o ke'oke'o [Hibiscus arnottianus ssp. immaculatus]. In Native Hawaiian plant information sheets. Lawai, Kauai: Hawaii Plant Conservation Center. National Tropical Botanical Garden. Unpublished internal papers.

Rauch, Fred D., Heidi L. Bornhorst, Rhonda Stibbe, and David Hensley. 1997. Oahu white hibiscus, Ornamentals and Flowers OF-22. Honolulu: Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. (Also available as a PDF file at Free CTAHR Publications.)

Wagner, Warren L., Darrel R. Herbst, and S. H. Sohmer. 1990. Manual of the flowering plants of Hawai'i. 2 vols., Bishop Museum Special Publication 83. Honolulu: University of Hawaii Press and Bishop Museum Press. p. 882-883.

Woolliams, Keith R. 1976. The propagation of Hawaiian endangered species. NATO Conference Series. I, Ecology 1:73-83.