A cultivated Vigna owahuensis vine, with the classic Fabaceae pea-like flowers, and trifoliate leaflets. An intact seed pod (fruit), seeds, and a curled seedpod displaying its dehiscent nature, which scatters seeds. Note this seedling with spider mite damage on older leaves, but on the newer leaves in the center, which are free of this pest after being treated with a miticide.

Growth Requirements

General

    Oʻahu vigna is one of the easiest native plants to grow. In fact, it will grow most anywhere there is good-draining soil and sunlight. If sowing seeds in containers, it appreciates a very well-drained soil with lots of black cinder, modest amounts of water, and very bright or preferably direct sunlight. Since it does not always transplant well, it is best to grow it from seeds.

    The seeds germinate in one to a few weeks, and vines grow rapidly, which is characteristic of many in the Pea family. Since it is a vine, you will want to provide some support for the plants to climb on. It can be a fence, shrubs, grasses, branches, twine or wire, a bamboo stake or the like--it's not picky. After flowering, if you wish to collect the seeds, you will need so before they split and scatter the seeds everywhere. I (Eickhoff) have been in working areas where the dehiscent pods decide it's time to burst open! And, like tiny pebbles being thrown, I've heard them hitting the siding on my house or a nearby ti (kī) leaf on a tree! Most anything can trigger them to open--the sun, the rain, brushing against the vine or a strong gust of wind. Seeds that are not collected will come up later when it rains or is watered, in a potted plant, flower bed, rock wall, or in sidewalk cracks. I have even found one sprouting from debris collected in the base of ti leaf.

    Though this beauty looks dainty, in reality, Oʻahu vigna is a tough vine that is drought, wind and heat tolerant.

Pests and Diseases

    Oʻahu vigna is very prone to attacks by spider mites. A miticide needs to be applied immediately when noticed, especially on seedlings, which can die in a couple of days. Slugs and snails will destroy the entire vine with a few bites. Refer to the Pests & Diseases page for ways to combat the above pests and diseases.  

Special Features and Information

General

    Oʻahu vigna (Vigna owahuensis) is a species of cowpea, belonging to the Pea family or Fabaceae. It is the only endemic species of Vigna in Hawaii and is federally listed as endangered. There is also an indigenous species native to Hawaii, nanea or mohihihi (Vigna marina), found in coastal sandy beaches in the islands [Wagner et al. 1990].

    Various closely related Vigna species are cultivated for food worldwide, including the shōzu or azuki bean (Vigna angularis), urad bean or black gram (V. mungo), rice bean (V. umbellata), mung bean (V. radiata), Chinese long bean (V. unguiculata subsp. sesquipedalis), and black-eyed pea (V. unguiculata subsp. dekindtiana).

Hawaiian Name

    There is no verified ancient Hawaiian name for Vigna owahuensis. The name Nanea has occasionally been used for this species, but we are not, as yet, aware of any references to confirm this. It may be that some have mistaken it for its yellow-flowered relative, Vigna marina, which does have Nanea as an accepted Hawaiian name. Therefore, we have not included it among the names listed in the opening text. Otto Degener, in his Books 1-4 compilation of Flora Hawaiiensis, referred to this species as Oʻahu vigna [Degener 1946]. While we always prefer to use Hawaiian names for native plants, this website has chosen to use the English vernacular name Oʻahu vigna for this species until a Hawaiian name is verified. 

Etymology

    The generic name Vigna is named in honor of Dominico Vigna (?-1647), a doctor, horticulturalist, and professor of botany at the University of Pisa, Italy [Wagner et al. 1990]. The specific epithet owahuensis has reference to an old spelling version (i.e., o-wahuensis) for the island of Oʻahu [O-Wahu]. The adjusted spelling now is owahuensis, without a dash (-), with -ensis added to Oʻahu to form a geographical epithet [Gledhill 2008].