Native Hawaiian Garden (7722)

Naio (Myoporum stellatum) – The raw material of evolution

The first time I saw a wild population of Myoporum stellatum, it was amazing. I was in Campbell Industrial Park (O‘ahu) trying to locate some remnant Achyranthes when I came across about three acres of unaltered naio shrubland. As I wandered through the shrubland avoiding the numerous sinkholes, what amazed me was that no two naio were exactly the same. Some had tiny flowers while others had flowers nearly half an inch across. Some had pure white flowers while others had flowers with purple throats or pink pokadots. Fruits were tiny or large (⅓ inch), round, ovoid or cigar-shaped. Leaves were short or long, wide or thin, serrated or smooth-edged. The shrubs themselves were sometimes dense and nearly spherical, perfect for someone’s front yard, while others had their branches twisted and stretching every which way. What I was looking at was the stuff all biology textbooks tell us is a prerequisite for evolution, phenotype variation (with presumably its genetic counterpart).

I had to share my discovery. So, because I was a Biology Instructor at Leeward Community College back then, I began taking my students out to the site once a semester to witness this diversity while they made field transpiration measurements and then, later, back at the College, determined stomatal density under the microscope. I took my students to this amazing place for two years until, to my horror, the entire site was bulldozed and nearly all the naio killed for no apparent reason. (The site was never built upon and, today, is a kiawe and Pluchea wasteland. Could there be people so evil as to destroy this place just to eliminate our visits?)

Habitat & Appearance: Myoporum stellatum once occupied much of the coastal zone of Kalaeloa and ‘Ewa, O‘ahu. And, until the 2005 brushfires, several plants also grew in the back of Nānākuli Valley. Today, there is only one known wild plant in Nānākuli Valley, and, because of rapid urban development, most of the plants in Kalaeloa and ‘Ewa are gone. A few years ago there was talk of designating this rare naio as a federally-listed endangered species but that never happened (suggesting that money still speaks louder than conscience). See above for a discussion on appearance.

Pokadot flowers, unripe and ripe fruits. Seedlings. Lantana lace bug with leaf damage. Naio thrips damage to Myoporum sandwicense, the other naio (Photograph from OISC webpage).

Naio in Hawaiian Culture: Naio (Myoporum sandwicense; maybe, M. stellatum) was a valuable wood in old Hawai‘i, used for net gauges, hale posts and framing (Krauss 1993). Near the end of the ‘iliahi trade (the early 1840s), 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 (Degener 1984).

Collecting Seeds: Naio flower frequently, so, it’s almost always possible to find ripe white fruit or slightly older brown fruit on the plant. Avoid unripe green fruit. Even older fruit on the ground beneath the plant will contain viable seeds but these must be cleaned and sterilized thoroughly (see below). After cleaning, the endocarp (with one to several fleshy, white, sausage-shaped seeds inside) can be stored for at least five years in the refrigerator.

Growing from Seed: Clean away the fruit’s fleshy exocarp and mesocarp leaving only the stony endocarp. If the fruits are old or were collected from the ground, sterilize them in 10% bleach for 15 minutes. Not all naio produce viable seeds. The way to check is to gently sand away the apex of the endocarp and look inside with a dissection microscope or hand-lens. What you will see is a few to several chambers. Inside each chamber is a seed. If the white seed is sausage-shaped, it’s likely good; if it is flat and shriveled, it is bad. After checking several endocarps and finding at least one good seed in each, take the remaining (non-sanded) endocarps and soak them for a few days in a shallow pan of clean water, changing the water each day. Then, sow the endocarps using Method One or Method Two.

I have always had very good germination success with Myoporum stellatum (much more so than with M. sandwicense). Seeds normally start sprouting about one month after sowing and continue for another couple of months. If you started the endocarps in a germination tray, transfer the seedlings to individual containers after they produce 2-3 true leaves. These little seedlings are pretty tough provided you avoid damaging the roots too much. I have transferred seedlings directly from one spot in the garden to another with a little care and a good watering. The seedlings are prone to attack by mealybugs, scale insects and mites; all will kill the small plants. Get rid of these pests with horticultural oil and/or a systemic insecticide.

Growing from Cuttings: If you have no luck with seed, cuttings are always an option. While individual naio vary in how easily they root from stem-tip cuttings, I’ve had success with all but one type I’ve tried (M. stellatum from Nānākuli Valley). Using either Method One (preferred) or Method Two, naio stem-tip cuttings take two weeks to three months to root sufficiently to remove them from the sealed container or mist chamber without wilting. After that, you’ll have a naio ready to plant in your garden in about 2-3 months.

Growth in the Garden: Despite its very limited range, Myoporum stellatum grows well in many different environments from sunny sandy coastlines through shaded calcified and clay soil lowlands to cloudy rocky cliffs over 1500 feet in elevation. This adaptability bodes well for native plant gardeners, giving you the flexibility to plant a naio almost anywhere in your garden; although, it will grow best in full sun. After a year, the naio will be two to three feet tall and beginning to flower and fruit. By three years, the shrub will be six or so feet in height and breath. This is near M. stellatum’s maximum size. My guess is that after reaching this size, the plant expends most of its energy on flowers, fruits and replacement leaves. Most naio grow into an attractive ball-shaped shrub. However, if you’re unhappy with its natural appearance, pruning is a viable option. Just be sure to make nice clean branch cuts; DO NOT go at it with a motorized hedge-trimmer!

M. stellatum naturally grows in very dry places with less than 20 inches of rain a year. Therefore, it’s okay to water your naio regularly (i.e., no more than once a week) for the first six months as it gets established in the garden but after that avoid overwatering (i.e., anything more than once a month). If you do overwater, you run the risk of killing your plant. I’ve seen this happen – very quickly – and guess it is likely due to a water-loving fungus attacking the roots.

Diseases & Pests: Less than ten years ago, I would not have hesitated recommending naio to anyone interested in adding this beautiful resilient shrub to their garden. (In fact, John and I did just that in our 1999 book!) However, today, the future of naio in Hawai‘i is seriously threatened by an introduced insect barely visible to the naked eye, the Myoporum or naio thrips (Klambothrips myopori). 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 (Big Island). In 2018, this terrible pest island-hopped to O‘ahu but has not yet been detected on any of the other Hawaiian Islands. If it does, we can only expect the naio on these islands will be equally devastated since, currently (2021), there is no effective method of halting or even slowing this plague on Hawai‘i and O‘ahu. While the thrips themselves are difficult to see, the damage they cause is quite recognizable. If you discover a naio that looks like the one in the bottom photograph here, call the Hawaii Pest Hotline at 643-PEST IMMEDIATELY! For more information on naio thrips visit the Hawaii Invasive Species Council webpage: https://dlnr.hawaii.gov/hisc/info/invasive-species-profiles/naio-thrips/.

Before Myoporum thrips, diseases and pests were a minor problem for anyone with naio in their garden. Yes, mealybugs or scale insects occasionally infest stem-tips, and every so often a stemborer kills a branch. However, I’ve never seen these attacks kill a naio, and, often, the problem disappears without treatment. Curiously, the most common pest of M. stellatum (but, not M. sandwicense) is the introduced lantana lace bug, Teleonemia scrupulosa. Introduced to Hawai‘i by one of my relatives, Albert Koebele, over a hundred years ago as a bio-control for the invasive lantana that was taking over cattle rangeland, the lantana lace bug jumped hosts (who knows when) and now attacks M. stellatum. Fortunately, these attacks are, in my experience, never fatal and easily managed. Infestations are most common during the dry hot summer and often disappear on their own with cooler wetter winter weather. If you don’t want to wait, several sprayings of horticultural oil about a week apart will kill this pest.

Ā ā Ē ē Ī ī Ō ō Ū ū