Hibiscus clayi
Malvaceae or Mallow family
Synonyms: Hibiscus newhousei
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Kokiʻo ʻula
Clay's hibsicus, Newhouse hibiscus
Natural Range & Environment
Hibiscus clayi is endemic to Kauaʻi. Historically, it's been found in scattered locations: Kōke‘e on the western side of the Island, Moloa‘a Valley in the north, Nounou Mountain (Sleeping Giant) in Wailua to the east, and as far south as Ha‘ikū [Ahupua‘a of Kaua‘i]. In 2017, a new population was discovered in the Moloa‘a Forest Reserve. When H. clayi was federally listed as endangered in 1994, there were only four known wild plants in the Nounou Mountains. However, subsequent explorations have found about 111 wild plants as of 2022. Additionally, this species has been cultivated for a long time, such that specimens can be seen around the world (mostly in botanical gardens). There is also an active restoration effort on Kauaʻi to protect the existing wild plants and to increase the size of the scattered populations with new plantings. Hibiscus clayi grows on slopes in dry to mesic forests from 9 to 765 m (30 to 2,510 ft) [USFWS;ECOS].
Hibiscus clayi has a one-day flower that can vary somewhat in the width of its petals (Photograph of thin-petal flower courtesy of Hectonichus CC BY-SA 3.0). Hibiscus clayi is distinguished from Hibiscus kokio, the other kokiʻo ʻula, by having a shorter calyx (the usually green or leafy outside part of a flower consisting of sepals) and little to no serrations on its leaves (Photograph of leaves and flower buds and header photograph courtesy of Forest & Kim Starr CC BY 2.0.). Hibiscus clayi can be used as an lone accent or to create an informal hedge.
Description
The endangered Hibiscus clayi is most commonly a shrub, rarely a small tree, with a lifespan well beyond five years. Its ovate to elliptic leaves can vary from a bit more than an inch (2.5 cm) to nearly four inches (10 cm) long, and are hairless and shiny on their upper surface and hairless (or nearly so) on their lower surface. Depending on the plant's origin, the leaf margin can be with or without serrations toward its tip. The absence of or limited leaf serrations of H. clayi is one of the features that distinguishes it from its close relative, H. kokio.
Large perfect (bisexual) flowers develop near the branch tips. These can vary a bit in petal shape and color, but are always some shade of red (unlike H. kokio, which has flowers from yellow to orange to red). The tubular calyx (i.e., all the sepals below the petals) is a bit more than half an inch to one inch (1.5 to 2.5 cm) long, in contrast to the calyx of H. kokio that is typically more than an inch (2.5 cm) long, and has five or six short bracts beneath it. Pollinated flowers develop into green 5-chambered capsules, turning pale brown and partially splitting open when ripe. Within each chamber are a few small slightly hairy brownish-black seeds. Hibiscus clayi blooms continuously in cultivation and (probably) in the wild [USFWS;ECOS].
We have encountered cultivated Hibiscus clayi that regularly set seed and others that never do so, and are uncertain about the cause(s) for this difference. It's possible that this species (or some individuals within the species) requires cross-pollination to set or produce viable seeds. It is also possible that some of the plants we thought were H. clayi were actually not, but instead infertile hybrids between H. clayi and some other Hibiscus species. Unfortunately or fortunately, depending on your point of view, the genus Hibiscus is well known for interspecies hybridization and for producing sterile hybrids. Regarding H. clayi, the differences in seed-setting behavior deserve professional investigation. Until then, you should be wary about where or from whom you obtain your native Hibiscus, and always ask the grower questions about the plant's origin (e.g., Did the parent/original plant come from a reliable source such as a botanical garden? Does the parent plant set seed? Was the plant propagated from a cutting, and, therefore, is a clone, or was it grown from seed?).
Growth Requirements
General
Hibiscus clayi is the most shrubby of Hawai‘i's native Hibiscus, and, therefore, unlike koki‘o ke‘oke‘o, it's unlikely you could use it as a shade tree. However, kokiʻo ʻula is a beautiful accent plant in your landscape, or planted in a line about three feet (1 m) apart, makes a unique native Hawaiian hedge. (Hibiscus clayi grows slower than the ubiquitous Chinese hibiscus; therefore, be sparing and gradual whenever pruning.) You can also keep Hibiscus clayi in a container; however, try to avoid having it become rootbound by transferring it to larger and larger containers as it grows.
Hibiscus clayi does best in a site with lots of sunshine and will grow in lava/cinder, clay, or organic-dominant soils, provided the soil drains well; we have not grown it in sand or coralline soil. It will also grow in partial or light shade, but is likely to produce fewer flowers than a plant grown in full sunlight for all or most of the day.
Generally, Hibiscus clayi needs less water than other native Hawaiian Hibiscus. How much exactly will depend primarily on where you plant it. In a hot dry lowland site, weekly watering is likely required, while in a cooler upland landscape, you may only need to water once a month or less. (Obviously, a container plant will require more frequent regular watering.) Fortunately, H. clayi is drought-tolerant and will normally "tell" you that it needs more water by dropping more and more of its leaves.
Kokiʻo ʻula has the disturbing behavior of dropping all its leaves when stressed. This can happen when it's first planted in the ground or when transferred to a larger container. Don't panic! Continue to water your plant regularly and closely monitor its stem tips. In most cases, your kokiʻo ʻula will recover and start putting out a new flush of leaves.
With lots of sunlight and adequate water, Hibiscus clayi grows at a moderate pace of about two feet (61 cm) a year. Most commercially available koki‘o ‘ula are propagated from cuttings, so flowers often appear soon after planting, even when the plant is small. If you've grown your koki‘o ‘ula from seed, you’ll have to wait a few years for the first flowers. If you see leaf yellowing or your koki‘o ‘ula doesn't seem to grow despite adequate sun and water, consider applying a single-digit major nutrients fertilizer with minor elements.
Most available Hibiscus clayi 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 ‘ula 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 ‘ula 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 clayi easily cross-pollinates with other hibiscus near them, 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 ‘ula 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 flower on a different Hibiscus clayi. 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 ‘ula leaves. Additionally, plants are occasionally attacked by all the usual sap-sucking insects: aphids, mealybugs and scale insects are normally concentrated at the stem-tips; spider mites and whiteflies are on the leaves. However, koki‘o ‘ula 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 these pests. Because ants often farm and defend the above-mentioned pests, it is sometimes necessary to control the ants as well to solve the pest problem long-term.
The hibiscus erineum mite or hibiscus leaf-crumpling mite (Aceria hibisci) seems to prefer the Chinese hibiscus over native species (Thank goodness!). However, koki‘o ‘ula is not immune (see photographs below). If you find this type of damage (i.e., leaves with pimples or other twisted distortions) on your koki‘o ‘ula, 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.
Hibiscus erineum mite damage on Hibiscus clayi. Second photograph also show lobate lac scale on the stem to the right. We don't yet know how deadly this new pest is for hibiscus. (Photographs courtesy of Scot Nelson public domain).
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 240 genera with approximately 4,220 known species [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].
In 1928, Albert W. Duvel discovered several small hibiscus trees on Kauaʻi, damaged by cattle, that he began cultivating. The hibiscus turned out to be a new species that Isa and Otto Degener named Hibiscus clayi in honor of the late Horace F. Clay, a horticulturalist and Instructor of Botany and Horticulture at Leeward Community College on Oʻahu [USFWS 1995]. Today (2025), there is a small garden containing Hibiscus clayi on the Leeward CC campus (north of the BS Building) honoring Horace Clay.
In 1959 and 1961, Sister Margaret James Roe, in her study of the genus Hibiscus in Hawai‘i, named Hibiscus newhousei as a new species of Hibiscus on Kauaʻi. However, today (2025), H. newhousei is considered a synonym of H. clayi [USFWS 1995].
Hawaiian Name
Kokiʻo is a generic name for some native Hibiscus species, as well as plants in the related native genus Kokia. ʻUla translates to "red" or "scarlet" [Pukui & Elbert 1986]. Aloalo is a generalized name Hawaiians gave to all the native Hibiscus species. The name kokiʻo ʻula is shared by two native Hawaiian red hibiscus, Hibiscus clayi and H. kokio.
Etymology
Hibiscus is the Latinized form of the Greek word ibiskoj or hibiskos from Virgil, hibiscum, for the marshmallow plant, Althaea officinalis [Gledhill 2008]. The species named by Isa and Otto Degener in 1959, clayi, honors Horace F. Clay, a horticulturalist and Instructor of Botany and Horticulture at Leeward Community College on Oʻahu [Federal Register 1991]. (see General above)
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