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Carex wahuensis subsp. wahuensis

leaf Main Plant Information

Genus

Carex

Species

wahuensis

Subspecies

  • wahuensis

Common Names

  • Oʻahu sedge

Synonyms

  • Carex nuptialis

Names with Unknown Sources

  • Oʻahu carex

leaf Plant Characteristics

Distribution Status

Endemic

Endangered Species Status

No Status

Plant Form / Growth Habit

  • Non-Woody, Clumping

Mature Size, Height (in feet)

  • Grass-like, Medium, 1 to 2.5
  • Grass-like, Tall, Greater than or equal to 2.5

Mature Size, Width

Oʻahu sedge has a spread of 2 feet or more.

Life Span

Long lived (Greater than 5 years)

Landscape Uses

  • Accent
  • Container
  • Erosion Control
  • Ground Cover

Additional Landscape Use Information

Carex of several species have been used as ornamental additions in landscapes on the mainland for the interesting, sometimes colorful, foliage and seedheads. A few species are now in cultivation in Hawaiʻi.

Oʻahu sedge is an excellent and tough accent plant. They can be use sparingly or en masse. A good non-invasive alternative for non-natives such as Umbrella sedge (Cyperus alternifolius).

They can be grown in containers in part to full sun with regular waterings. [1]

Source of Fragrance

  • No Fragrance

Plant Produces Flowers

Yes

leaf Flower Characteristics

Flower Type

Not Showy

Flower Colors

  • Brownish
  • Green
  • Red
  • Yellow

Additional Flower Color Information

Oʻahu sedge has either green to yellowish green or reddish brown to dark red diminutive flowers.

Blooming Period

  • Year Round

Additional Blooming Period and Fruiting Information

This sedge is a perennial. While the flowers are not attractive, the stalks of yellow seeds somewhat resemble small corn cobs and are a nice feature in the landscape.

leaf Leaf Characteristics

Plant texture

  • Coarse

Additional Plant Texture Information

The leaves are no smaller than 6 to 15 inches and as large as 40 inches long.

Leaf Colors

  • Dark Green

Additional Leaf Color Information

Leaves have sharp teeth along the edges.

leaf Pests and Diseases

Additional Pest & Disease Information

Oʻahu sedge can attract ants, scale, thrips, mealy bugs and aphids.

leaf Growth Requirements

Fertilizer

Light applications of a balanced slow release fertilize with minor elements every six months is suggested. Foliar feeding 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 monthly has proven beneficial. [David Eickhoff, Native Plants Hawaiʻi]

Pruning Information

None required except to trim off dead leaf and stem material. Trim off flower spikes (achenes) if you want the plant to last years longer. However, the flowering spikes are one of the nicer features to this sedge.

Water Requirements

  • Dry

Additional Water Information

Once plant is established, water only during prolonged drought. Plants can tolerate moist conditions, but does best in drier conditions.

Soil must be well drained

Yes

Light Conditions

  • Full sun
  • Partial sun
  • Shade

Additional Lighting Information

Overall appearance of this sedge is nicest when grown in partial shade.

Spacing Information

For thick a groundcover, Oʻahu sedge can be planted every 1 to 2 feet apart or randomly spaced for a more natural appearance.

Tolerances

  • Drought
  • Wind

Soils

  • Clay
  • Cinder
  • Organic

Limitations

Most sedge leaves have sharp teeth along edge. As the saying goes "sedges have edges."

They are only somewhat salt spray tolerant.

leaf Environmental Information

Natural Range

  • Kauaʻi
  • Oʻahu
  • Molokaʻi
  • Lānaʻi
  • Maui
  • 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)

Habitat

  • Terrestrial

Additional Habitat Information

Oʻahu sedge are known to grow in dry to mesic forest, mesic to subalpine shrubland and sometimes coastal forests usually on ridges, slopes and gulches or rocky substrate.

leaf Special Features and Information

General Information

There are about 2,000 species of Carex worldwide, more than any other genus in the Sedge family or Cyperaceae. Half of the eight species of Carex native to the Hawaiian islands are endemic or naturally found nowhere else.

Carex wahuensis has three recognized subspecies:

  • subsp. wahuensis is commonly seen from 1475 to 3280 feet in elevation on all of the main islands except Niʻihau and Kahoʻolawe.
  • subsp. herbstii is rare and known from a single collection from Moanalua Valley, Oʻahu at around 1180 to 1210 feet.
  • subsp. rubiginosa is found at 1675 to over 8200 feet primarily on Maui and Hawaiʻi Island, but also at a few scattered sites on Kauaʻi, Oʻahu, Molokaʻi, and Lānaʻi from about 785 to 1970 feet.

Etymology

The generic name Carex is the classical Latin name for sedge, pehaps from carere, to be absent, as the upper spikes are staminate (male) and do not produce seeds.

The specific epithet wahuensis is an old spelling variation referring to the island of Oʻahu.

The subspecies name herbstii named after Derral R. Herbst, botanist.

The subspecies name rubiginosa, rusty.

Early Hawaiian Use

None of the eight native species appear to have any known Hawaiian names. Certainly the people knew these of interesting sedges and perhaps had uses for them.

Modern Use

Seed spikes are rather unique and can be added to cut flower arrangements. [David Eickhoff, Native Plants Hawaiʻi]

Additional References

[1] "Container Gardening in Hawaii" by Janice Crowl, page 52.

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