Myoporum sandwicense subsp. sandwicense
Scrophulariaceae or Figwort family (formerly in Myoporaceae)
Synonyms: Myoporum fauriei, Myoporum sandwicense, Myoporum sandwicense var. fauriei, Myoporum sandwicense subsp. st.-johnii, Myoporum st-johnii, Polycoelium sandwicense
Naio
Naeo, Naieo
Bastard sandalwood, False sandalwood
Natural Range & Environment
Myoporum sandwicense is endemic to all the main Hawaiian Islands, but is extinct on Kaho‘olawe (but see below). It can be seen from sea level to 3,000 m (9,843 ft) [Flora of the Hawaiian Islands]. It has a wide geographic and ecological range on the Islands, being found naturally in coastal areas, drylands, mesic to wet forests, and is a dominant plant in some subalpine areas such as the saddle region between Mauna Kea and Mauna Loa on Hawai‘i Island [Chinnock 2007].
Myoporum sandwicense was divided into two endemic subspecies in 2007: subsp. sandwicense (on all the main Hawaiian Islands but now extinct on Kaho‘olawe) and subsp. lanaiense (restricted to the northern part of Lānaʻi in dry koaiʻa forests) [Chinnock 2007].
Myoporum sandwicense is on the Kaho‘olawe Island Reserve Commission (KIRC) 1998 Restoration Plan's list of shrubs to be outplanted. Our AI search revealed a 2017 Forest & Kim Starr photograph showing that such plantings did occur, but we are (currently) unable to elaborate on their current extent or status.
Leaves, flowers, and fruits of a coastal naio on Maui. An increasingly popular (before 2009) prostrate form of naio, originally from Hawai‘i Island, but planted here along the Kāʻanapali Beach Walk on Maui (Coastal naio, Beach Walk naio, and header naio [at Auwahi, Maui] photographs courtesy of Forest & Kim Starr CC BY 3.0). Myoporum thrips (Klambothrips myopori) damage to Myoporum sandwicense (Photograph from OISC webpage). The possible future of Myoporum sandwicense — a cultivated plant in San Anton Gardens on the island nation of Malta, currently free of Myoporum thrips (Photograph courtesy of Silvio Scicluna ©)? Without photographs like this one of Professor John B. Hall standing next to a massive dead trunk, we might not believe that huge naio trees once populated our forests (Photograph courtesy of G.D. Carr ©).
Description
Myoporum sandwicense displays considerable variation in morphology. However, most of these differences are between geographically separate populations rather than between individual plants within a population. For example, all the coastal M. sandwicense on O‘ahu are short to tall shrubs that have pointed glossy hairless dark green leaves and mostly-white flowers and fruits with varying amounts of pink to purple tinting. Contrast this with a form growing high above in the Wai‘anae Mountains that is nearly always ten or more feet (3 m) tall and usually has dull green leaves.
Myoporum sandwicense has a lifespan well in excess of five years and some may be ancient before they die (see photograph above). Naio populations can be composed of shrubs all less than two feet (61 cm) tall to those populated by trees more than 20 feet (6 m) tall. Naio bark is gray; the bark of large trees is thick and furrowed or scaly. Its wood is light yellow, relatively soft, and has a lemony fragrance that endures long after the plant has died. In addition to their wood, living naio often emit a spicy or honey-like fragrance. We're not certain where this odor originates, its leaves, flowers, or fruits.
Most naio have lance-like leaves about three inches (8 cm) long and half an inch (1.3 cm) wide, but there is a lot of size variation depending on the population and environmental conditions. The leaves can have a margin that is serrated (common in young plants) or completely smooth, and be hairless to quite hairy, glossy to dull, and leathery (common in coastal forms) to paper-like. Naio leaves are usually clustered at the stem tip.
All Myoporum sandwicense have small perfect (bisexual) five-point tubular flowers (four- and six-point flowers are rare) that are most often entirely or partially white. When not completely white, pink to purple accents (e.g., spots) in the throat of the flower are most common. Naio blooms nearly all year round, particularly cultivated plants, with some wild plants pausing during periods of drought. The small fleshy fruits are normally white (rarely hinted with other colors) when ripe. They are bitter to us; however, birds will actively seek out and eat the ripe fruits. The stony endocarp has several chambers. Inside each is either a tiny white cigar-shaped and viable seed or a shriveled non-viable seed. It's not uncommon for a naio to produce fruits with no viable seeds within them.
Growth Requirements
General
In the early 2000s, Myoporum sandwicense was becoming an increasingly popular landscape plant in Hawai‘i. In particular, a glossy-leaf prostrate form from Hawai‘i Island had entered the commercial market and was becoming a favorite of hotels, shopping centers, and residents. That all changed in 2009 when the alien Myoporum thrips (Klambothrips myopori), native to Tasmania, was accidentally introduced to Hawai‘i Island from California, where it had already decimated the ornamental Myoporum (M. laetum and M. pacificum) there. The State quickly began eradication efforts, removing infested and sometimes uninfested naio, in an attempt to curb the spread of this lethal pest. Unfortunately, despite these efforts, the tiny insect island-hopped to O‘ahu in 2018, continuing to disfigure and kill both cultivated and wild Myoporum sandwicense alike. Following the spread to O‘ahu, State efforts shifted from eradicating infested plants on the two Islands to trying to prevent the thrips from spreading further to the remaining Hawaiian Islands using monitoring and interisland inspections and restrictions.
Currently (2025), the State continues to encourage the public not to plant naio. However, we have an alternative recommendation for those of you willing to put in the extra time and effort. Past is the time of planting and trying to maintain a multi-plant naio groundcover or hedge, particularly one using a form like the once-popular prostrate naio (which was especially hard-hit by the Myoporum thrips). Rather, we encourage you (again, only if you can put in the effort and are willing to remove and destroy your naio if it is beyond saving) to grow one or two of the lesser-known forms of naio in an effort to discover thrips-resistant varieties of Myoporum sandwicense and help secure naio's future in Hawai‘i. Following are our recommendations with this goal in mind.
Try to obtain a naio form or variety that is uncommon or shows some anecdotal evidence of Myororum thrips resistance. For example, some growers have reported that fuzzy naio seem to be faring better than hairless forms. Naio can be propagated from cuttings, so this makes it easier to obtain these less common forms from other like-minded native Hawaiian plant enthusiasts.
Be prepared and comfortable to use insecticides; if you're not, you probably should not attempt this naio project. So far, safe sprays like insecticidal soap and horticultural oil, as well as contact insecticides like malathion, have been only marginally effective at controlling Myoporum thrips because the insects live between and are protected by the distorted leaves they create. Therefore, pruning and destroying infested branches along with using systemic insecticides has been more effective. See additional control information below in Pests and Diseases. To date (2025), there are no known biocontrols for Myoporum thrips; however, scientists in both Hawai‘i and California are working hard to find them.
You should grow only one or two naio (at one time) so you can easily accommodate the monitoring and care they will require. Also, keeping them in a container will allow you greater control than planting them in the ground. However, keep the container outside so your naio is potentially exposed to Myoporum thrips; we can't discover resistant varieties if we all keep our naio inside.
Place your naio in a site that receives full sunlight for all or most of the day. Myoporum sandwicense has a very wide geographic range within the Islands, so how much water your plant will need will depend on where it originally came from. Coastal and lowland forms are generally xeric and require very little watering (e.g., once or twice a week if kept in a container), while upland forms from mesic or wetter forests will likely need daily watering; if planted in the ground, lessen these watering requirements to once a week or not at all depending on your local rainfall. Regardless of the amount of water your form of naio needs, all forms require easily draining media. Therefore, fill your container with 25% to 50% black cinders or perlite. Likewise, an in-the-ground plant needs soil that easily drains away water.
Naio generally grows quickly in the ground and begins flowering within a year or two. In a container, expect them to grow more slowly and eventually become (non-fatally) stunted if not occasionally transferred to a larger container. Container naio benefit from biannual applications of a balanced controlled-release fertilizer with minor elements or monthly foliar feeding with an organic or inorganic water-soluble fertilizer diluted to ⅓ to ½ the recommended strength. Naio in the ground do not require fertilizer.
Monitor your naio regularly for Myoporum thrips and act immediately if you see any evidence of their presence. Remove and destroy any infested branches, and treat the plant with a systemic insecticide if you haven't already. Spraying with horticultural or neem oil can also help — a little — by deterring the thrips from hopping to other branches. Record your efforts and keep informed. Hopefully, a biocontrol agent will be found, and you'll want to know asap. Lastly, share your experiences (and cuttings from your uncommon naio forms) with others.
Pests and Diseases
Before Myoporum thrips, diseases and pests were minor problems for anyone with naio in their landscape. Overwatered plants would sometimes get a black sooty mold growing on their leaves. And aphids, mealybugs, scale insects, or spider mites would occasionally infest a plant's stem-tips, or a black twig borer would kill a branch. However, we never saw these attacks kill a naio, and, often, the disease or pest would disappear without treatment. Refer to the Pests & Diseases page for ways to deal with each of these pests if they do not go away on their own.
Today, the future of naio in Hawai‘i is seriously threatened by the Myoporum or naio thrips (Klambothrips myopori), an introduced insect barely visible to the naked eye. Accidentally introduced around 2009, probably hitching a ride on landscape plants imported from California, Myoporum thrips have decimated most of the wild and nearly all of the cultivated naio (Myoporum sandwicense) on Hawai‘i Island. In 2018, this terrible pest island-hopped to O‘ahu and attacked both naio species. In 2024, naio thrips were detected on Moloka‘i, and, in 2025, they were found on Kaua‘i [Hawaii Invasive Species Council].
Currently (2025) there is no effective method of halting this plague. While the thrips themselves are difficult to see, the damage they cause is quite recognizable (see the photograph above). For more information on Myoporum thrips, visit the Hawaii Invasive Species Council Naio Thrips page or the Oʻahu Invasive Species Committee (OISC) webpage. Immediate pruning and destruction of infested branches and systemic insecticides are currently the best treatments we have against this deadly pest. Unfortunately, there are few systemic insecticides available in Hawai‘i and even fewer sold in most local garden shops (i.e., those containing imidacloprid or spinosad). Check out this University of California IPM site for more information on chemical controls for Myoporum thrips.
Uses
Ancient Hawaiian
Hawaiians called naio (Myoporum sandwicense; maybe, M. stellatum) wood ʻaʻaka [Pukui & Elbert 1986]. It was used for net needles and hale posts [Krauss 1993]. Holmes [1981] noted that naio wood was used to make the bow and stern ornamental end pieces (manu) and gunnels of canoes. And, Lennox [1967] wrote it was, “Used for house timbers, fishing torches.” Early on and near the end of the ‘iliahi trade (1790s to 1850s), the fragrant wood of naio was sometimes passed off as sandalwood. However, the Chinese quickly realized the deception and the plant acquired the unflattering name, bastard or false sandalwood [Merlin & VanRavenswaay 1991].
Modern
There is a small commercial market for naio wood oil which is used in aromatherapy diffusers; cosmetics; potpourri; massage oils; bath oil and, as a perfume body oil [Natural Alchemy].
Special Features and Information
General
The Figwort family or Scrophulariaceae has around 60 genera and 1,830 species worldwide [WikipediA;Scrophulariaceae].
There are three recognized endemic species of Myoporum in Hawai‘i: the common Myoporum sandwicense (formerly found on all main Hawaiian Islands but now extinct on Kaho‘olawe), and two rare species: M. degeneri (endemic to dry forests from ʻUlupalakua to Kaupo Gap, East Maui), and M. stellatum (ʻEwa Plains and Nānākuli Valley, Oʻahu). The populations of Myoporum outside the Hawaiian Islands, naturally found on Mangaia (Auʻau Enua) in the Cook Islands, were formerly classified as Myoporum sandwicense. These plants are now classified as a distinct species, Myoporum wilderi, locally called ngaio and restricted to Mangaia, but also cultivated on Rarotonga by the Indigenous people who use the flowers to scent coconut oil [Chinnock 2007].
Myoporum sandwicense was divided into two endemic subspecies in 2007: subsp. sandwicense (on all main Hawaiian Islands but now extinct on Kaho‘olawe) and subsp. lanaiense (restricted to the northern part of Lānaʻi in dry koaiʻa forests) [Chinnock 2007]. We have never seen the subspecies lanaiense and are not taxonomists; therefore, we're unable to comment on any significant morphological or horticultural characteristics or differences between the two subspecies.
Hawaiian Name
All native Myoporum species in Hawai‘i are referred to as naio. This is also the name for a parasitic pinworm (Enterobius sp.), a type of seaweed, and an inferior kalo left in the field after harvest [Pukui & Elbert 1986].
Etymology
Myoporum is derived from the Greek myo, meaning "close," and poros, meaning "pore," in reference to the close appearance of the leaf glands of these plants [Wagner et al. 1990]. The species and subspecies name, sandwicense, refers to the "Sandwich Islands," as the Hawaiian Islands were once called and named by James Cook on one of his voyages in the 1770s. James Cook named the islands to honor John Montagu (The fourth Earl of Sandwich) for supporting Cook's voyages [Gledhill 2008].
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