Hibiscus arnottianus
subsp. arnottianus,
subsp. immaculatus,
& subsp. punaluuensis
Malvaceae or Mallow family
Synonyms:
Subspecies arnottianus: Hibiscus arnottianus, Hibiscus arnottianus f. parviflorus, Hibiscus waimeae var. hookeri
Subspecies immaculatus: Hibiscus immaculatus
Subspecies punaluuensis: Hibiscus arnottianus var. punaluuensis, Hibiscus punaluuensis
Kokiʻo keʻokeʻo
All Subspecies: Aloalo, Hau hele, Kokiʻo kea, Pāmakani
All subspecies: White rosemallow
Subspecies arnottianus:
Oʻahu white hibiscus
Subspecies immaculatus:
Molokaʻi white hibiscus
Subspecies punaluuensis:
Oʻahu white hibiscus, Punaluʻu hibiscus, Punaluʻu white hibiscus
Natural Range & Environment
Hibiscus arnottianus subsp. arnottianus and subsp. punaluuensis are endemic to Oʻahu. Subspecies arnottianus is the more common and widespread of the two subspecies, being found in dry to mesic forests from 120 to 790 m (394 to 2,592 ft) in both the Wai‘anae Mountains and the eastern end of the Ko‘olau Mountains from Wahiawā to Nui Valley. Subspecies punaluuensis is restricted to the Ko‘olau Mountains, where it is seen in mesic forests from 200 to 700 m (656 to 2,297 ft) from Kaipapa‘u to Waiāhole [Wagner et al. 1990].
The rare Hibiscus arnottianus subsp. immaculatus is endemic to east Moloka‘i and is federally listed as endangered. It was found historically from Waihānau Valley east to Pāpalaua Valley. Currently (2023), it grows at Pelekunu, Waiehu Cliffs, and Wailau, in mesic to wet forests from 15 to 480 m (49 to 1,575 ft), scattered along steep sea cliffs. USFWS [2023] estimates there are currently from 150 to 300 wild plants, along with 85 restoration plantings. Stored seeds and ex-situ plantings are also part of the State's recovery efforts.
Subspecies arnottianus flowers and cultivated shrub (Shrub photograph courtesy of Forest & Kim Starr CC BY 3.0 US). Subspecies immaculatus flower and cultivated shrub. Subspecies punaluuensis flower and leaves (Photograph courtesy of Mashuri Waite CC BY-NC 4.0). David Hoppe-Cruz next to a mature kokiʻo keʻokeʻo (subspecies arnottianus) in dry forest (Wai‘anae kai, O‘ahu). (Header photograph courtesy of Forest & Kim Starr CC BY 3.0 US.)
Description
Hibiscus arnottianus is a large shrub to large tree (see photographs above) in the wild with a lifespan well beyond five years. However, its growth potential is often unrealized in cultivation because of regular pruning (see comments below in Growth Requirements). Kokiʻo keʻokeʻo has gray bark, and its wood is white and brittle (except for its youngest branches).
Subspecies arnottianus has ovate hairless (or nearly so) leaves up to four inches (10 cm) long with sometimes entire, sometimes toothed, margins; leaves may sometimes have red veins. Subspecies immaculatus differs by sometimes having leaves that are slightly larger, being pubescent (hairy) on their lower surface, and having a scalloped margin. Subspecies punaluuensis leaves are typically much larger than those of the other two subspecies, up to 10 inches (25 cm) long, with coarsely pubescent upper and lower surfaces.
All three Hibiscus arnottianus subspecies have large white five-petal perfect (bisexual) flowers. They can be distinguished from one another by differences in the color of the flower's central reproductive column and the size of the flower's bracts (small modified leaves at the base of the flower). Additionally, while the flowers of subspecies arnottianus and punaluuensis normally last about two days, those of subspecies immaculatus typically last a single day [Huppman 2013]. Both subspecies arnottianus and punaluuensis have a red reproductive column, while the column of subspecies immaculatus is white. Comparing subspecies arnottianus and punaluuensis, the bracts at the base of a punaluuensis flower are about twice as long (10 to 25 mm) as those of arnottianus.
Hibiscus arnottianus flowers are slightly to very fragrant and, along with H. waiameae, are supposedly the only known natural species of Hibiscus with fragrant flowers. The fragrant flowers have led biologists to speculate that native moths may be (were) the primary pollinators of koki‘o ke‘oke‘o [Huppman 2013]. Cultivated kokiʻo keʻokeʻo bloom nearly year-round but may stop for a short period, usually during the winter or early spring months. Pollinated flowers develop into dry tan five-chambered capsules with each chamber holding a few fuzzy brown angular seeds.
Growth Requirements
General
There are a few cultivars of Hibiscus arnottianus commercially available because of their hardiness, abundance of flowers, or particular flower form, with subsp. arnottianus and immaculatus being the most commonly seen subspecies in cultivation. About half of our experiences growing H. arnottianus are with these cultivated varieties.
Like other hibiscus, Hibiscus arnottianus is a versatile plant for landscaping and can be used as an accent, to create a hedge or screen, or to provide shade. It can also be kept as a container plant. While we like to describe kokiʻo keʻokeʻo as "a shrub that wants to become a tree," this doesn't mean you have to let it become one. Kokiʻo keʻokeʻo tolerates gradual pruning, a few branches at a time, quite well, allowing you to shape the plant into the form you want. If you desire a bushy shrub, concentrate your pruning on removing or shortening the central, most vertical branches. If, instead, you want your kokiʻo keʻokeʻo to become a tree as quickly as possible, prune away the lower side branches, and, over time, work your way up. Kokiʻo keʻokeʻo grows fast, but not super fast. Therefore, if you decide to make/let your kokiʻo keʻokeʻo become a tree, understand that you're engaging in a decade(s) long project. Obviously, any dead or diseased branches should also be consistently removed.
Hibiscus arnottianus does best in a site with a lot of sunshine. However, it will grow in partially or lightly shaded sites but may produce fewer flowers. Subspecies punaluuensis seems to be the most shade-tolerant and may even grow better in the shade when planted in a hot dry location. Koki‘o ke‘oke‘o grows best in lava/cinder, clay, or organic-dominant soils, provided the soil drains well.
How much you need to water your koki‘o ke‘oke‘o will depend primarily on where it originally came from and where you plant it. A koki‘o ke‘oke‘o from the dry forests of the Wai‘anae Mountains will require less watering than a plant originating from Mānoa in the Ko‘olau Mountains. Similarly, koki‘o ke‘oke‘o planted in a hot dry lowland site will likely require weekly watering, while the same plant in a cooler upland landscape may only need to be watered once a month or less. (Obviously, a container plant will require more frequent regular watering.) If you don’t know your plant’s origin, you’ll have to experiment and observe the plant until you discover its needs. Fortunately, all koki‘o ke‘oke‘o can tolerate slight to moderate drought, providing you with enough time for your plant to "tell" you, with wilted or dropped leaves, that it needs more water.
With lots of sunlight and adequate water, koki‘o ke‘oke‘o grows quickly, reaching three or more feet (1 m) tall in a year. Most commercially available koki‘o ke‘oke‘o are propagated from cuttings, so flowers often appear soon after planting, even when the plant is small. If you have grown your koki‘o ke‘oke‘o from seed, you’ll have to wait 2 to 3 years for the first flowers. If you see leaf yellowing or your koki‘o ke‘oke‘o doesn't seem to grow despite adequate sun and water, consider applying a single-digit major nutrients fertilizer with minor elements.
Most available Hibiscus arnottianus are propagated from cuttings to ensure genetic identity (i.e., it is a clone of the parent plant). These plants never develop an anchoring taproot, typical of a koki‘o ke‘oke‘o grown from seed, and this can be a problem during a wind and/or rainstorm because the secondary roots cannot prevent the shrub from toppling over. To prevent this from happening, select a planting site that's protected from strong winds and regularly hand-prune your koki‘o ke‘oke‘o to prevent it from becoming top-heavy. If your shrub still falls over, assess the damage, remove any damaged branches, and decide on whether to let the plant recover as is or reposition and support it with stakes and ties. Generally, if many of the roots have been uprooted and exposed, it's best to reposition, reroot, and support the shrub; if not, leave the plant as is unless you find it too unsightly.
Hibiscus arnottianus easily and frequently cross-pollinates with other hibiscus near it, producing hybrid seeds. Therefore, it's safest to only create new plants by rooting stem cuttings. If you still decide to collect seeds from your koki‘o ke‘oke‘o to grow new plants, you should hand-pollinate bagged flowers. Do this by enclosing the flower in a paper bag before it blooms. When the flower blooms, open the bag and hand-pollinate it with some pollen, preferably from a different flower on a different plant of the same subspecies. Re-close the bag around the flower, wait a week, and then remove the bag.
Pests and Diseases
Chinese rose beetles and grasshoppers sometimes get a taste for koki‘o ke‘oke‘o leaves. Additionally, plants are occasionally attacked, usually at or near the stem-tips, by all the usual sap-sucking insects: aphids, mealybugs, scale insects, and whiteflies. However, koki‘o ke‘oke‘o is a resilient plant, and attacks by these pests are almost never fatal. We normally wait for natural predators like ladybird beetles, lacewings, and mealybug destroyers to find and eliminate these pests. However, if the infestation doesn’t disappear on its own, or you just don’t want to wait, refer to the Pests & Diseases page for ways to deal with each of the above-mentioned pests.
The hibiscus erineum mite or hibiscus leaf-crumpling mite (Aceria hibisci) seems to prefer the Chinese hibiscus over native species (Thank goodness!). If you find this type of damage (i.e., leaves with pimples or other twisted distortions; see Hibiscus clayi for photographs of damage) on your koki‘o ke‘oke‘o, remove and discard the affected leaves or branches. If the problem persists, you can first try several sprayings of horticultural oil (about a week apart) before resorting to commercially available miticides. Miticides are tricky. Some are only available to licensed pest exterminators. Check out your local garden shop, and ask them what’s available to you for combating the erineum mite. Be sure to read and follow the label directions since miticides are often only effective if the application protocol is followed exactly.
Koki‘o ke‘oke‘o are occasionally infected by bacterial leaf spot (Pseudomonas spp.); see Nelson [2011] for description and photographs. If you see these lesions on your plant, remove all the affected leaves and reduce your watering schedule. In particular, avoid getting the leaves wet when watering (e.g., turn off the sprinklers and water by hand), which will spread the disease to healthy leaves. Alter your fertilizing schedule, increase or decrease, to see if this helps eliminate the disease. If possible, move or alter the immediate environment around your koki‘o ke‘oke‘o to provide it with more sunlight and wind (i.e., make the site drier). While there are bactericides to combat leaf spot, these are not always effective and modifying the plant's environment is a safer long-term solution.
Uses
Ancient Hawaiian
Both the native red and white Hibiscus were cultivated near homes for their flowers, which were used for both ornamental and medicinal purposes [Kepler 1995]. However, often these written references only use the more generic name for native Hibiscus, kokiʻo or aloalo, and, therefore, it is currently impossible to describe species-specific uses.
Kokiʻo was traditionally prepared by pounding it with other plants, straining the juice, and consuming it for purification purposes. The leaves were chewed and ingested as a natural laxative, while mothers would chew the buds and give them to infants and children for the same purpose [McDonald & Weissich 2003]. Additionally, mothers would chew the buds and give them to children, or children would consume the seeds to help strengthen a weak child. The beautiful flowers were skillfully crafted into stunning lei, but unfortunately, these only lasted a day [Handy & Handy 1972]. The bark of aloalo was likely used to make cordage (inferior to hau), but supportive written accounts are scarce. For example, Krauss (1993) mentions that "hibiscus" was used in her chapter on fiber craft.
Modern
Like the introduced Chinese hibiscus, native Hibiscus flowers are often used for decoration, such as placing a flower behind one's ear.
Special Features and Information
General
The large Mallow family, Malvaceae, contains about 4,200 species, with notables such as okra, cacao, durian, baobab, kenaf, and cotton [WikipediA;Malvaceae]. There are currently seven native species of Hibiscus recognized in the Hawaiian Islands, with all but two considered endemic [Flora of the Hawaiian Islands].
Koki‘o ke‘oke‘o, Hibiscus arnottianus and H. waimeae, are highly prized by plant breeders because they are supposedly the only natural Hibiscus species with a fragrant flower.
Huppman 2013, based on her DNA research, has suggested that all three subspecies of Hibiscus arnottianus be given full species status as Hibiscus arnottianus, H. immaculatus, and H. punaluuensis.
Hawaiian Name
Kokiʻo kea and Kokiʻo keʻokeʻo translate to " the white kokiʻo" and "the very white kokiʻo," respectively [Pukui & Elbert 1986]. Kokiʻo is a more generic name for some native Hibiscus species, as well as plants in the related native genus of Kokia. Aloalo is a generalized name Hawaiians gave to native Hibiscus species. Hau is the name of a hibiscus (Hibiscus tiliaceus) that is either indigenous to Hawai‘i or introduced by early Polynesian explorers [Wagner et al. 1990]. Hau hele translates as "traveling hau" [Pukui & Elbert 1986], a name similar to ma‘o hau hele, another native Hawaiian Hibiscus. (See Hibiscus brackenridgei for an explanation regarding its Hawaiian name.) Somewhat oddly, Hibiscus arnottianus also has the Hawaiian name pāmakani, a name it shares with a completely unrelated species of native Hawaiian violet (Viola chamissoniana).
Etymology
Hibiscus is the Latinized form of the Greek word ibiskoj or hibiskos from Virgil, hibiscum, for the marshmallow plant, Althaea officinalis [Gledhill 2008]. According to Gledhill [2008], the species and subspecies name, arnottianus, is mostly likely in honor of George Arnott Walker Arnott (1799–1868), a Scottish botanist, traveler, collector, and professor of botany at the University of Glasgow [WikipediA;George Arnott Walker Arnott], or (less likely) named for David Arnot (1821–1894), a South African naturalist [S2A3]. The subspecies name, immaculatus, means "unblemished, immaculate, without spots" [Gledhill 2008], most likely referring to the white reproductive column of this subspecies' flower. The subspecies name, punuluuensis, refers to the area where this subspecies is found, Punaluʻu in the Koʻolau Mountains of Oʻahu.
BPK