Notelaea sandwicensis small flowers are clustered at the tree's leaf bases. Shiny leaves of a mesic forest olopua on O‘ahu. Dull leaves and unripe fruits of a dry forest olopua on Maui. (Dry forest olopua tend to have duller — less shiny — and thicker leaves than mesic forest olopua.) The trunk of this old wild olopua is deeply corregated (Photograph courtesy of Kenneth R. Wood CC BY-NC 4.0). Ripe olopua fruits are dark purple to black. An old wild tree at Auwahi, Maui. (Photographs of flowers, leaves and unripe fruits, ripe fruits, and wild Maui tree courtesy of Forest & Kim Starr CC BY 2.0.)

Growth Requirements

General

    Until recently, our ability to acquire and successfully germinate Notelaea sandwicensis seeds has limited our horticultural experiences with this beautiful tree. Further uncertainty about olopua's landscape potential is fueled by the fact that we only know of one long-lived (about ten years old) tree in a cultivated setting, specifically, in a friends' yard in upland Maui. This tree is now twelve feet (3.7 m) tall and produces flowers and fruit. Therefore, it may be that olopua does best in cooler upland settings. Still, given these caveats, we encourage other native Hawaiian plant enthusiasts, if given the opportunity, to add this species to their collection as either a container plant or an accent in their landscape. Here is what we know so far.

    Notelaea sandwicensis grows best in a site with full sunlight for all or most of the day, but is tolerant of some shading. It can be grown with other dry forest plants like ‘alahe‘e, lama, and uhiuhi, but requires more watering than these species. It will also grow with more mesic native plants such as ‘iliahi, ‘ōhi‘a lehua, and palapalai. In both settings, growth is slow (less than a foot a year) and often sporadic. While olopua seems to prefer slightly moist soil, it cannot survive in constantly wet or poor-draining soil. Older wild trees are tolerant of drought, but this may be misleading — perhaps, they have deep roots keeping them hydrated — since many of our new olopua plantings at restoration sites have died during extended dry periods.

    Olopua does well as a container plant, and, given its slow growth and the current scarcity of horticultural knowledge regarding this species, a container may be the safest place (for now) to grow olopua. The slow growth also means fewer pot-to-pot transfers!  

    Avoid pruning olopua, except to remove dead branches and stems. Young olopua, in the ground or in a container, will benefit from the application of a balanced controlled-release fertilizer with minor elements every six months.

Pests and Diseases

    Olopua is sometimes attacked by scale insects, mealybugs, and thrips, which are often protected and farmed by ants. The black twig borer devastated wild olopua populations in the latter half of the 1900s, so much so, that many of the surviving trees look more like shrubs today because of the repeated attacks. Refer to the Pests & Diseases page for methods to combat these pests.  

Special Features and Information

General

    The taxonomy of Oleaceae is messy and requires further molecular and traditional study. Currently, most botanists estimate the family to contain approximately 600 species within about 30 genera, with a nearly cosmopolitan distribution but best represented in Asia and Malesia. Several species are either well-known or economically important, such as olives (Olea spp.), forsythia (a popular early-flowering shrub), ash (Fraxinus spp.) used for timber, and jasmine (Jasminum spp.) made into perfume. Locally, pīkake (Jasminum sambac), a name also used for peacocks with both the flower and the bird being favored by Princess Ka‘iulani, is a popular flower for lei [Wagner et al. 1990]. 

    Olopua is the only native Hawaiian plant in the Olive family, and is a common host to Hawai‘i's endemic tree snails. 

Hawaiian Name

    The Hawaiian name for olopua flowers is nonohina [Pukui & Elbert 1986].

Etymology

    Notelaea is derived from the Greek word notos, meaning "southern," and elaia, meaning "olive." It is a reference to the genus' predominant occurrence in the Southern Hemisphere [Stearn 1995]. The former genus name, Nestegis, is possibly derived from the Greek ne, meaning "not," and stegos, meaning "cover," likely a reference to the lack of a corolla in the type species, Nestegis elliptica [Wagner et al. 1990]. The species name, sandwicensis, 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].