Branched inflorescence with flower buds (see closeup of tiny flowers in header). The inedible (bitter) fruits of lonomea look a bit like dates. Hawaiians strung together the glossy seeds of lonomea in lei. Lonomea leaves (with small inflorescence) typically have a prominent yellow midrib (Photograph courtesy of thatplantguy CC BY-NC 4.0). This 16-year-old cultivated lonomea is the perfect shade tree. A dense stand of relatively young wild trees in the Wai‘anae Mountains of O‘ahu (Photograph courtesy of MIke Ross CC BY-NC 4.0). 

Growth Requirements

General

    Sapindus oahuensis is probably the best native shade tree Hawai‘i has to offer. You can also keep lonomea in a container even though it will ultimately become (non-fatally) root-bound and stunted, much like those ubiquitous Ficus trees commonly seen in hotel lobbies and outside store entrances. Is it too obvious to say that you should plant or place this native shade tree in a site that gets full sunlight all or most of the day?

    How fast a lonomea grows and how big it gets when planted is almost entirely dependent on how much water it receives. In a location: (1) with regular rainfall totaling about 40 inches (102 cm) or more per year, or (2) near a stream, or (3) with frequent watering (i.e., once a week or more), lonomea will grow very quickly to become a large tree, 30-plus feet (9 m) tall and more than a foot (30 cm) in diameter at its base, in about 15 years. Conversely, in a location with less than 30 inches (76 cm) of rain per year and no one watering it, a lonomea will likely be less than 20 feet (6 m) tall in the same amount of time. Add to this dry site a fair amount of wind and your lonomea can be nearly as wide as it is tall (see the photograph of a 16-year-old tree above). Lonomea are drought tolerant and will start dropping leaves to let you know it "wants" more water. Cultivated lonomea begin flowering and fruiting at 5 to 10 years of age.

    Since lonomea has the potential to become a large tree, avoid planting it near your house, other structures, or where you park your car. It's not the tree's roots you have to worry about. They seem to be rather benign, and we've never seen lonomea roots crack a foundation, sidewalk, etc. Rather, the concern is lonomea's brittle wood that can break during a strong windstorm, causing a large branch to come crashing down.   

    Lonomea is not fussy about soil type and will grow in cinder/lava, clay, organic-dominant, and even coralline and sandy soils, provided (of course) the soil drains water well. When young, in addition to watering, you can speed the growth of your lonomea by applying a balanced controlled-release fertilizer with minor elements every six months or spraying your tree's leaves monthly with an organic or a water-soluble inorganic fertilizer diluted to ⅓ to ½ the recommended strength. Adult trees, generally, do not need to be fertilized.

    Large lonomea generate a significant amount of leaf and fruit litter. The leaves and fruits that fall onto the ground quickly decompose (except for the seeds which gradually sink into the soil, unlike the ankle-busting fruits and seeds of kukui) and can improve the soil. However, we recommend not planting lonomea near your swimming pool or pond to avoid the hassle of continuous leaf and fruit removal. 

    Lonomea tolerates moderate hand-pruning. Do so to remove dead branches, fruit clusters, water shoots at its base, or problematic branches you fear may break during a windstorm.

Pests and Diseases

    Lonomea planted in windless areas are prone to whitefly infestations and attack by a small gray weevil (Myllocerus sp.); control the weevil with weekly sprayings of insecticidal soap or once every few months with a systemic insecticide. The leaves of small trees are sometimes chewed on by Chinese rose beetles. Fortunately, the leaves of larger trees are normally too high for the rose beetles to reach. Stressed lonomea are vulnerable to attacks by black twig borers and false powderpost beetles. Refer to the Pests & Diseases page for ways to combat each of the above-mentioned pests.

Special Features and Information

General

    The Soapberry family (Sapindaceae) has about 1,860 species in 138 genera. Well-known non-Hawaiian family members include maples, horse chestnut, ackee, and the locally popular lychee [WikipediA;Sapindaceae]. Native members include the closely related indigenous mānele (Sapindus saponaria), as well as the endangered endemic māhoe (Alectryon macrococcus), and the common indigenous ʻaʻaʻliʻ (Dodonaea viscosa).

    Soapberry fruits contain the chemical saponin, a type of natural detergent that foams when mixed with water. This makes them a natural and eco-friendly alternative to synthetic detergents. However, while saponins are useful for cleaning, they are also slightly toxic if ingested, and, therefore, should not be accidentally consumed when washing [Cornell].

Hawaiian Name

    Hawaiians used the name lonomea for Sapindus oahuensis on Kauaʻi, while on O‘ahu, the tree was called āulu or kaulu, names also used for other native Hawaiian plants. Today, lonomea is the dominant name used throughout the State. Lamb (1981) notes the additional name keulu, likely just a spelling alternative of kaulu. 

Etymology

    The genus name, Sapindus, is derived from the Latin words, sapo, meaning "soap," and indicus, meaning "Indian," [Gledhill 2008] likely referring to the use of soapberry trees in India for soap. The species name, oahuensis, refers to the island of Oʻahu, one of the two islands where this species is naturally found. The suffix -ensis was added to Oʻahu to Latinize the name [Gledhill 2008].