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Eleocharis obtusa

leaf Main Plant Information

Genus

Eleocharis

Species

obtusa

Hawaiian Names with Diacritics

  • Kohekohe
  • Pīpīwai

Hawaiian Names

  • Kohekohe
  • Pipiwai

Common Names

  • Blunt spikerush
  • Spikerush

leaf Plant Characteristics

Distribution Status

Indigenous

Endangered Species Status

No Status

Plant Form / Growth Habit

  • Non-Woody, Clumping

Mature Size, Height (in feet)

  • Grass-like, Short, Less than 1

Mature Size, Width

Kohekohe has about a 1-foot spread.

Life Span

Short lived (Less than 5 years)

Landscape Uses

  • Accent
  • Container
  • Erosion Control
  • Ground Cover
  • Water Features

Additional Landscape Use Information

Even though this species of kohekohe is found at higher elevations, it does very well at near sea level locations in pots or man-made ponds. Kohekohe is an attractive water loving rush that is popular with growers and is a natural groundcover controlling erosion in wet situations. Because of its small size, height and its clumping habit it is a great plant for small water features. [David Eickhoff, Native Plants Hawaiʻi]

Source of Fragrance

  • No Fragrance

Plant Produces Flowers

Yes

leaf Flower Characteristics

Flower Type

Not Showy

Flower Colors

  • Brownish
  • White

Additional Flower Color Information

Kohekohe has multiple tiny whitish-brown flowers. The spikelets are characterized by their obtuse, or blunt, form.

Blooming Period

  • Year Round

Additional Blooming Period and Fruiting Information

These are annuals. The tiny brown seeds (dark yellow in E. erythropoda; black in E. geniculata) can be harvested for future plantings or allowed to regenerate in the same pot or water feature. Consumption by waterfowl also spreads seeds naturally.

leaf Leaf Characteristics

Plant texture

  • Coarse

Additional Plant Texture Information

Kohekohe leaves range from 12 to 16 inches long.

Leaf Colors

  • Light Green

leaf Pests and Diseases

Additional Pest & Disease Information

Kohekohe is prone to ants, scale, thrips, mealy bugs, and aphids.

leaf Growth Requirements

Fertilizer

In containers that hold water, some fertilizer is appreciated but be cautious of too much nitrogen which can produce green algae in water especially in warm summer months. None necessary in large water features such as fish ponds. The plants will receive nutrient needs from the watery habitat it grows in. Never use fertilizer in any natural wetlands sites. [David Eickhoff, Native Plants Hawaiʻi]

Pruning Information

Dead leaf material may be trimmed as needed with sharp pruners or heavy scissors.

Water Requirements

  • Wet

Additional Water Information

Kohekohe is best grown in wet to very wet settings. It can also be grown with roots totally submerged in water and is popular as an attractive clumping pond or water feature plant. [David Eickhoff, Native Plants Hawaiʻi]

Soil must be well drained

No

Light Conditions

  • Full sun
  • Partial sun

Additional Lighting Information

Kohekohe is best grown in full sun for optimal growth.

Spacing Information

This spikerush is a clumping species as oppose to the rhizome nature of of some others (E. erythropoda). For a thick covering, plants should be spaced 6 to 8 inches apart. Otherwise, plants should be spaced 1 foot apart to showcase this charming little rush. [David Eickhoff, Native Plants Hawaiʻi]

Tolerances

  • Waterlogged Soil
  • Wind

Soils

  • Organic

Limitations

As an annual, kohekohe is short lived but self seeds for regeneration. Some plants will perform more like perennials than annuals. [David Eickhoff, Native Plants Hawaiʻi]

leaf Environmental Information

Natural Range

  • Kauaʻi
  • Oʻahu
  • Molokaʻi
  • Maui
  • Hawaiʻi

Natural Zones (Elevation in feet, Rainfall in inches)

  • 150 to 1000, Greater than 100 (Wet)
  • 1000 to 1999, Greater than 100 (Wet)
  • 2000 to 2999, Greater than 100 (Wet)
  • 3000 to 3999, Greater than 100 (Wet)
  • 4000 to 4999, Greater than 100 (Wet)

Additional Habitat Information

Naturally, this Eleocharis occurs from 1280 to over 6200 feet in elevation and found in wet areas, bogs, ponds, along streams and other wet places. This indigenous rush is also found in temperate North America.

leaf Special Features and Information

General Information

The 120 or more species of spikerushes (Eleocharis spp.) belong to the Sedge family or Cyperaceae. Kohekohe are generally water loving plants with some growing in mesic environments. The Hawaiian Islands have one, possibly two, indigenous species and at least four naturalized species.

Perhaps the most well known of the spikerushes is the Chinese water chestnut (Eleocharis dulcis) in which the tubers on the rhizomes are either cooked or eaten raw. In Fiji and Niuafoʻou in Tonga, this species is called kuta and the stems are plaited into soft sleeping mats, and perhaps used to some degree in the past in Samoa, where it is called ʻutuʻutu. [1]

Rush or Sedge? Though rushes and sedge belong to the same family (Cyperaceae), there is a simple way to distinguish one from another: the stem-like leaves (culms). Rushes have round, cylindrical stems or leaves, sometimes hollow like a drinking straw if cut open. Sedges have triangular, often sharp-edged leaves. Just remember: "rushes are round; sedges have edges."

Etymology

The genus name Eleocharis comes from Greek helos, "of the marsh or meadow," and charis, "grace, favor, or loveliness."

The specific epithet obtusa is from the Latin obtuse or blunt in reference to the blunt seed head of this species.

Background Information

Kohekohe (Eleocharis obtusa) is one of the few native rushes. A robust variety (E. obtusa var. gigantea) with larger floral features is rare.

Early Hawaiian Use

Medicinally, kohekohe (Eleocharis spp.) was used to treat puʻupuʻu wela (unknown?), pūhō (abscess, burst sore, ulcer), and ʻaʻai (spreading sores). The plants were processed by cooking and then used to wash affected areas. [2]

Additional References

[1] "Plants of the Canoe People" by W. Arthur Whistler, pages 24, 107.

[2] "Native Hawaiian Medicine--Volume III" by The Rev. Kaluna M. Kaʻaiakamanu, page 63.

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