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Vigna o-wahuensis

leaf Main Plant Information

Genus

Vigna

Species

o-wahuensis

Common Names

  • Oʻahu cowpea
  • Oʻahu vigna

Synonyms

  • Vigna owahuensis
  • Vigna sandwicensis

Names with Unknown Sources

  • Nanea

leaf Plant Characteristics

Distribution Status

Endemic

Endangered Species Status

Federally Listed

Plant Form / Growth Habit

  • Non-Woody, Spreading

Mature Size, Height (in feet)

  • Herbaceous, Short, Less than 1
  • Herbaceous, Medium, 1-3
  • Herbaceous, Tall, Greater than 3

Mature Size, Width

This is a vine that grows to approximately 4 to 16 inches long. The above "Mature Size" is based on its vining nature.

Life Span

Short lived (Less than 5 years)

Landscape Uses

  • Container
  • Ground Cover
  • Trellis or Fence Climber

Additional Landscape Use Information

These rare native vines can be annual or perennial, but are best grown as an annual since they are easy to grow and spread rapidly. They grow well on wire or wood fencing, on shrubs, and even up into trees that provide enough sunlight. An easy to grow vine if pests such as red spider mite can be kept under control.

Due their nature of broadcasting seeds (dehiscent) from the pod, they often appear in the oddest places, such as a crack in the sidewalk, on a rock wall, in an open pipe, or some other debris-filled crevice! Because of the dehiscent force, you may hear the seeds hit objects such as the siding on the house or a metal object in the area. So be sure to collect the seed pod turn brown and woody before this blessed event happens. [David Eickhoff, Native Plants Hawaiʻi]

Source of Fragrance

  • No Fragrance

Plant Produces Flowers

Yes

leaf Flower Characteristics

Flower Type

Not Showy

Flower Colors

  • Green
  • Yellow

Additional Flower Color Information

Oʻahu vigna has clusters of one to four thin translucent pale yellow or greenish yellow flowers.

Blooming Period

  • Sporadic

Additional Blooming Period and Fruiting Information

Oʻahu vigna is an annual or perennial. The ripe brown furry seed pods are dehiscent ...that means they are explosive! and can broadcast seeds several feet away throughout the yard or landscape. As mentioned, seedlings will appear in rainy weather or when the area is watered, sometimes in cracks in rock walls or concreted areas. [David Eickhoff, Native Plants Hawaiʻi]

leaf Leaf Characteristics

Plant texture

  • Fine
  • Medium

Additional Plant Texture Information

Leaves are up to 3 inches long and are sparsely or moderately covered with course hairs. [2] There is much variation in leaf shape, size and texture among this species.

Leaf Colors

  • Light Green
  • Medium Green

leaf Pests and Diseases

Additional Pest & Disease Information

These vines are often attacked by both spider mites and leaf miners. [David Eickhoff, Native Plants Hawaiʻi]

Slugs can also be a problem. [Rick Barboza, Hui Kū Maoli Ola]

leaf Growth Requirements

Fertilizer

These nitrogen-fixing vines require no additional nitrogen in fertilizer. Foliar feeding monthly in early morning with a water-soluble or an organic fertilizer (e.g. kelp or fish emulsion) at one-third to one-fourth the recommended strength has proved beneficial. [David Eickhoff, Native Plants Hawaiʻi]

Pruning Information

Unless plant is vining into unwanted areas, pruning is not necessary. After the plants flower, collect ripe seed pods before the burst, and remove dead vines if needed. [David Eickhoff, Native Plants Hawaiʻi]

Water Requirements

  • Dry

Additional Water Information

After the plant is established, water weekly if the weather is dry.

Soil must be well drained

Yes

Light Conditions

  • Full sun
  • Partial sun

Additional Lighting Information

For optimal results, it should be planted in full sunlight.

Spacing Information

Plant every 1 to 3 feet apart. The vines will grow together. Seeds planted on location often may offer better results than transplanting the vines. [David Eickhoff, Native Plants Hawaiʻi]

Tolerances

  • Drought
  • Wind
  • Heat

Soils

  • Cinder
  • Organic

Special Growing Needs

Plants should be provided with other shrubs, a trellis, or a fence to climb on.

leaf Environmental Information

Natural Range

  • Niʻihau
  • Oʻahu
  • Molokaʻi
  • Lānaʻi
  • Maui
  • Kahoʻolawe
  • Hawaiʻi

Natural Zones (Elevation in feet, Rainfall in inches)

  • Less than 150, 0 to 50 (Dry)
  • 150 to 1000, 0 to 50 (Dry)
  • 1000 to 1999, 0 to 50 (Dry)
  • 2000 to 2999, 0 to 50 (Dry)
  • 3000 to 3999, 0 to 50 (Dry)
  • 4000 to 4999, 0 to 50 (Dry)

Additional Habitat Information

A very rare and seldom seen vine known to grow primarily in dry grassland and shrubland from 30 to about 4500 feet.

It is presumed to be naturally extinct on Niʻihau and Oʻahu, which is ironic given the common name Oʻahu vigna and Latin species name o-wahuensis, an older written form of Oʻahu [O-Wahu].

leaf Special Features and Information

General Information

Oʻahu vigna (Vigna o-wahuensis) is one of three Vigna species or Cow peas native to the Hawaiian Islands and a member of the Pea family or Fabaceae. This the only endemic species and federally listed as endangered.

There are, or were, two other indigenous species native to Hawaiʻi: the extant, that is still existing, nanea or mohihihi (Vigna marina), and wild pea (V. adenantha) now apparently extinct in the Hawaiian Islands, but existing elsewhere in the Pantropics.

Several closely related vigna species are grown for food worldwide. Among them are 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). [3]

Etymology

The generic name Vigna is named in honor of Dominico Vigna (?-1647), doctor, horticulturalist and professor of botany at the University of Pisa, Italy.

The specific epithet o-wahuensis has reference to an old spelling version for the island of Oʻahu [O-Wahu].

Background Information

Common names currently used for this wonderful species are Oʻahu vigna or Oʻahu cowpea. [1,2]

Early Hawaiian Use

Early Hawaiians were very aware of the plants and animals around them and most certainly knew of this species. But no Hawaiian name is yet known for this delicate endemic vine.

Additional References

[1] "Flora Hawaiiensis" by Otto Degener, Family: 169c Vigna Owahuensis
[2] "Recovery Plan for Multi-Island Plants" by USFWS, pages 1, 158, 159.
[3] http://en.wikipedia.org/wiki/Vigna [accessed 10/10/08]

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