Native Hawaiian Garden (7722)

Nā‘ū or Nānū (Gardenia brighamii) … and then there was one*.

Mo‘olelo and historical accounts suggest that Hawai’i’s endemic gardenia, the nā‘ū or nānū, was a common tree in the dry lowland forests of all the main islands before the 1900s. Not so today. Now, only a handful of wild trees are still alive on Lāna‘i along with one known tree on O‘ahu. Not too long ago, the summer of 2001 to be exact, there were four wild nā‘ū (although we only knew of three at the time) on O‘ahu, two in Nānākuli Valley and one at Pu‘u Ku‘ua. That year, a small band of botanists including myself hiked into the south branch of Nānākuli Valley to see how the two trees were faring. As you can see from the photograph, they were not well. In fact, the smaller of the two (not pictured) had died that very year, most likely losing a long competition for water with the six-foot-tall guinea grass surrounding it. After 2001, I visited the remaining nā‘ū once or twice a year with small groups of volunteers. We removed the grass from its tiny enclosure and secured weedcloth along the interior perimeter.

Over time, the tree’s health improved so that it produced enough fruit that we were able to give Lyon Arboretum about 300 seeds for long-term storage. Unfortunately, the two brushfires of 2005 that scorched two-thirds of the Valley ended those visits. The fire was so intense that, even though there was no grass to burn around it and the tree itself was untouched, the heat alone killed the nā‘ū. The following year, I heard from friends that the nā‘ū at Pu‘u Ku‘ua had died, presumably from a long battle with alien insects. However, not all was lost because near the end of 2001, on an exploratory hike into the north branch of Nānākuli Valley with Joel Lau, Joel discovered a new wild tree, bigger than the nā‘ū killed in the 2005 fire.

While the tale above is tragic, as you probably know, you don’t need to go all the way to Lāna‘i or hike to the back of Nānākuli Valley to see a nā‘ū. Rather, you need only go to your nearest botanical garden (Koko Crater has some nice trees) to see this beautiful tree. Additionally, you can buy your own nā‘ū at many public plant sales and native plant nurseries.

Meanwhile, we are making some progress at nā‘ū reforestation. The State’s PEP program has established a test planting of nā‘ū in Wai‘anae, while at KFI’s Nānākuli Valley Cultural & Botanical Preserve and Ka‘ala Kipuka, we have about two dozen healthy nā‘ū, some more than ten years old and beginning to flower. Fortunately, because of the horticultural and cultural value of this beautiful endemic tree, complete extinction of the nā‘ū seems unlikely. I wish I could say the same for some of its “uglier” companions.

*A Sad Update (2023): The last wild nā‘ū on O‘ahu, the one discovered by Joel Lau in 2001, has died.

Habitat & Appearance: Nā‘ū are small to average-sized trees of the native dry lowland forest and shrublands with shiny dark green leaves and white fragrant flowers about one inch in diameter. While very rare in the wild today, we think they once existed on all the main Hawaiian Islands, and before human habitation probably grew in many of the places we occupy today (e.g., Honolulu, Kailua-Kona). Nā‘ū fruits are green (greenish-grey or greenish-yellow when ripe) and about the size of a golf ball. Currently, there is debate as to whether or not nā‘ū is strictly dioecious (separate male and female plants). I suspect not. Rather, based on my observations, some plants may be only female or only male while others (like the Nānākuli nā‘ū) are capable of producing viable seeds without a male partner.

Visit to Nānākuli nā‘ū in 2001. Nā‘ū flower and fruit. Ripe nā‘ū fruit split open to show orange pulp and seeds (Photograph courtesy of Forest & Kim Starr CC BY 2.0). Nā‘ū seedlings in cage field experiment. Three-year-old nā‘ū at Preserve.

Nā‘ū in Hawaiian Culture: Nowadays, we usually think of colors in terms of light — for example, the colors of the rainbow or the RGB of a video screen. However, not all indigenous peoples thought or spoke of colors the same way. One example is how Hawaiians describe many colors; did you know that there is no direct Hawaiian translation for the English word “blue”? Often a Hawaiian color word is also the word for the origin of that color. Nā‘ū is an example, which, if you look it up in a Hawaiian dictionary, not only is the name of the Hawaiian gardenia (Gardenia brighamii), but is also the word describing the color of the dye Hawaiians extracted from the ripe flesh of its fruits.

In ancient times, Hawaiians also fashioned nā‘ū wood into kua lā’au (kapa anvil). And, of course, the flowers were a favorite for lei. People with a better nose than me tell me that the nā‘ū has a sweeter less citrus fragrance than the more frequently cultivated Tahitian or tiare gardenia.

Collecting Seeds: Nā‘ū fruits and seeds take a long time to mature – six to twelve months. Test to see if the fruit is ripe by squeezing it; if the flesh is soft, it is ripe. After picking the fruit, you should be able to easily break through the segments of the eggshell-like endocarp to expose the bright orange seeds inside. Handwash the seeds, discarding any that float. Nā‘ū seeds can be stored in the refrigerator for at least ten years without much loss in viability.

Growing from Seed: If the seeds are fresh, sow them directly in clean media without pretreatment. If they have been stored for a while, soak them overnight in a shallow pan of water before sowing. The seeds take 2-6 weeks to germinate. Transfer the seedlings to individual pots when they have 2-4 true leaves. Mites, scale insects, and mealybugs often attack seedlings; any of these can kill if not dealt with. Often these can be removed with a cotton swap moistened with alcohol. For more serious infestations, spray the plants with an appropriate insecticide (see Enemies in the Garden). You can hasten the growth of your young nā‘ū with any standard slow-release or foliar fertilizer. The plants should be ten inches tall in about six months, ready to be transferred into your garden.

Growing from Cuttings: I’ve never had much success growing nā‘ū from cuttings but others have. Most important seems to be the condition of the plant you’re taking the cutting from. The nā‘ū should be healthy and actively growing; avoid any plant with droopy leaves, pests, disease, or other signs of stress. Take terminal cuttings about 8 inches long, remove the lower leaves, and treat with rooting hormone. The people I know who have had success place their cuttings under a mist system and then wait months for roots to develop. Of course, the one big advantage of cuttings over seeds is you will not have to wait years for your nā‘ū to flower. For this reason alone, it’s worth at least one attempt.

Growth in the Garden: Nā‘ū grows at a reasonable rate of about one foot per year. Remember, they are small trees, and, in their early years, are more shrub-like than straight-up trees. As I’ve hinted, you’ll need to be patient waiting for flowers from a nā‘ū grown from seed. Most of my plants did not start flowering until they were at least five years old. And, fruiting usually takes another couple of years. While you can quicken the plant’s growth with fertilizers, do not overwater your nā‘ū. In fact, once it is established in the ground, I recommend you never water your nā‘ū.

Diseases & Pests: The biggest killer of nā‘ū I’ve seen in cultivation is overwatering. The plant’s leaves will be wilted, so the owner will water it. The leaves wilt even more, so the owner waters it again. Pretty soon it’s dead. Remember, this is a dry forest tree. And, it is really well adapted to drought. Therefore, if the leaves are wilted or falling off the tree, chances are, it is not a water problem but more likely a pest or disease attacking the roots. Root mealybugs are the worst. The nā‘ū’s leaves will wilt, yellow or fall off, and by the time you notice the mealybugs just beneath the soil at its base, it’s probably too late. Fortunately, a frequent clue before things get this bad is the presence of ants that farm the mealybugs. Therefore, maintain a vigil for ants on or near the base of your nā‘ū. If you see them, get rid of them with an insecticide right away. Then, treat the plant with a systemic insecticide to kill any unseen mealybugs. Nā‘ū are also attacked by mealybugs (and scale insects) above ground, on the leaves and stems. This attack is usually not as deadly but, just the same, should be dealt with quickly with appropriate insecticides.

Ā ā Ē ē Ī ī Ō ō Ū ū