Wild Ipomoea imperati are almost always seen in sandy habitats (Photograph courtesy of U.S. Fish & Wildlife Service, public domain). Hunakai can extend beneath the sand to cover a large area (Photograph courtesy of Texas Parks & Wildlife Department [Brenda Bowling] ©). A cultivated plant with flowers and differing leaf shapes. 

Growth Requirements

General

    Ipomoea imperati is normally easy to grow and maintain in a landscape (but see Pests and Diseases below) and will stay very low to the ground; it is not a climbing vine. However, you should give hunakai room to spread since it is sometimes passively aggressive and can pop up in unexpected places. Hunakai grows best in coastal landscapes in sand or sandy soils but will also grow in other soil types provided they drain well (e.g., soils with a high percentage of cinder or crushed coral). Its habit of burrowing through the sand and frequently rooting at its nodes makes it an excellent choice for stabilizing sandy shorelines. However, because of its diffuse and cyclic growth habit, hunakai is not a good choice as a weed-controlling groundcover. Hunakai can also be kept as a container plant; fill the container with sand or a mix of sand and crushed coral.

    Plant hunakai in a site with full sunlight for all or most of the day, since shaded plants generally do not grow well or will not flower as frequently. Once established, water your hunakai only during periods of prolonged drought. Hunakai is tolerant of extreme heat, drought, strong winds, salt spray, or even infrequent brief exposure to seawater. 

    While not required, hunakai will 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 recommended strength. Occasionally, spraying hunakai with seawater also seems to help with growth and pest management. Avoid pruning hunakai unless it unwantedly invades nearby planting areas.

Pests and Diseases

    Hunakai is sometimes attacked by the sweet potato weevil (Cylas formicarius). Since crop rotation, one of the most effective prevention methods for dealing with this pest, is not an option for hunakai plantings, other control means must be attempted. Systemic insecticides like imidacloprid can be used (but avoid treatment when hunakai is flowering because imidacloprid is deadly to bees). Other, less toxic treatments, such as spraying with horticultural oil or seawater, can also reduce weevil damage. Fortunately, because hunakai roots frequently at its nodes, it has been our experience that plants will go through cycles of weevil infestation in which the plant(s) die back (or even disappear for a time) followed by a period of regrowth and reappearance from unaffected underground nodes, possibly because natural predators, diseases, or environmental conditions have (temporally) eliminate the weevils. Hunakai is also occasionally infested by spider mites. Refer to the Pests & Diseases page for ways to deal with spider mites. 

Special Features and Information

General

   There are more than 1,650 species within about 60 genera in the Morning glory family (Convolvulaceae), distributed worldwide [WikipediA;Convolvulaceae]. Hunakai is related to some locally popular food plants such as ʻuala or sweet potato (Ipomoea batatas) and ung-choi or swamp cabbage (Ipomoea aquatica).

    In addition to Ipomoea imperati, native Hawaiian members of Convolvulaceae include: the endemic and endangered Bonamia menziesii; the indigenous makihi (Cressa truxillensis); the endemic and parasitic kauna ʻoa (Cuscuta sandwichiana); the indigenous koali ʻawa (Ipomoea indica), White-flowered beach morning glory (I. littoralis), and pōhuehue (I. pes-caprae subsp. brasiliensis); the endemic Hawaiian moon flower (I. tuboides); and the endemic pāʻu-o-hiʻiaka (Jacquemontia sandwicensis).

    Hunakai is related to some locally popular food plants such as ʻuala or sweet potato (Ipomoea batatas) and ung-choi or swamp cabbage (Ipomoea aquatica).

Hawaiian Name

    Hunakai translates as "sea foam" [Pukui & Elbert 1986], appropriate for its shoreline habitat. The name is shared with the sanderling (Calidris alba), a migratory shorebird that quickly runs across the receding waves on sandy shores in search of food (i.e., small marine animals) [Hawaii Audubon Society 2021]. 

Etymology

    Ipomoea is derived from the Greek words ips, for "worm," and homoios, meaning "similar to," a reference to the species' twining habit [Wagner et al. 1990]. The species name, imperati, possibly comes from Ferrante Imperato (1550–1625), an Italian botanist from Naples, and author of Del l’historia naturale (1599) [Gledhill 2008], or is derived from the Latin word imperator, meaning "commander or emperor" [Wisdom Library].