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Wilkesia gymnoxiphium

leaf Main Plant Information

Genus

Wilkesia

Species

gymnoxiphium

Hawaiian Names with Diacritics

  • Iliau

Hawaiian Names

  • Iliau

Common Names

  • Kauaʻi greensword
  • Kauaʻi wilkesia
  • Wilkesia

Synonyms

  • Argyroxiphium gymnoxiphium

Names with Unknown Sources

  • Nakedsword

leaf Plant Characteristics

Distribution Status

Endemic

Endangered Species Status

No Status

Plant Form / Growth Habit

  • Shrub

Mature Size, Height (in feet)

  • Shrub, Small, 2 to 6
  • Shrub, Medium, 6 to 10
  • Shrub, Tall, Greater than 10

Life Span

Long lived (Greater than 5 years)

Landscape Uses

  • Accent
  • Specimen Plant

Additional Landscape Use Information

Botanist and conservationist Otto Degener (1899-1988) said that this "is a magnificent plant, worthy of cultivation."

Degener was right! Iliau 'are indeed worthy of cultivation' and rather easy to grow and maintain. Despite their natural higher elevation habitat, they can be grown even near sea level. Iliau adds another and different landscape feature with the leaf and stalk texture.

Source of Fragrance

  • Leaves

Additional Fragrance Information

Towards the evening, iliau gives off a slight, pleasant scent, closely resembling that of a ginger flower. [Rick Barboza, Hui Kū Maoli Ola]

Plant Produces Flowers

Yes

leaf Flower Characteristics

Flower Type

Showy

Flower Colors

  • Cream
  • Greenish-White

Additional Flower Color Information

Plant produces 30 to 225 florets per head with cream-colored flowers.

Blooming Period

  • June
  • July

Additional Blooming Period and Fruiting Information

In its natural environment iliau blooms in June and July, fruiting a month later. [1] This awesome plant, however, only blooms once at the end of its life span of around 7 years or so and then completely dies. [Rick Barboza, Hui Kū Maoli Ola] The blooming display is nothing less than spectacular!

leaf Leaf Characteristics

Plant texture

  • Coarse

Additional Plant Texture Information

Iliau leaves are fuzzy and somewhat tacky. The leaves range from 6 to 20 inches long. Iliau does not branch except if injured.

The leaves are interesting and uniquely arranged in numerous arrangements called a "sheathing base." A sheathing base may have from four to fifteen leaves all characteristic joined at the base similar to what might be described as a square-heeled foot with very long toes.

Leaf Colors

  • Light Green

Additional Leaf Color Information

The leaves are light green with a gray or silver cast.

leaf Pests and Diseases

Additional Pest & Disease Information

Iliau is prone to leafminers, ants, spittle bugs, and root nematodes.

leaf Growth Requirements

Fertilizer

Apply a balanced slow release fertilize with minor elements every 6 months. Foliar feed monthly with a kelp or fish emulsion, or a water-soluble fertilizer with a dilution of one-half to one-third of the recommended strength. [David Eickhoff, Native Plants Hawaiʻi]

Pruning Information

None required except to remove the brown spent leaves which are easy to peel off the stalk.

Water Requirements

  • Dry

Additional Water Information

Water once a week for a month until it is established and then only during a prolonged drought. Despite the delicate appearance of iliau, the plants do not rquire much water and will do fine with deep waterings a few times a month in hot, dry weather. [David Eickhoff, Native Plants Hawaiʻi]

Soil must be well drained

Yes

Light Conditions

  • Full sun

Tolerances

  • Drought
  • Wind

Soils

  • Cinder

Limitations

Sad to say: Iliau does die after flowering but is still well worth adding to the landscape, if only for the attractive foliage alone. The final flowering is the just the thick icing on a really awesome cake! (See comments under Additional Blooming Period Information)

leaf Environmental Information

Natural Range

  • Kauaʻi

Natural Zones (Elevation in feet, Rainfall in inches)

  • 1000 to 1999, 0 to 50 (Dry)
  • 1000 to 1999, 50 to 100 (Mesic)
  • 2000 to 2999, 0 to 50 (Dry)
  • 2000 to 2999, 50 to 100 (Mesic)
  • 3000 to 3999, 0 to 50 (Dry)
  • 3000 to 3999, 50 to 100 (Mesic)

Habitat

  • Terrestrial

Additional Habitat Information

The spectacular plant is endemic to Kauaʻi. Iliau occurs on dry ridges or in open sites in dry to mesic forests from about 1400 to 3600 feet.

leaf Special Features and Information

General Information

Iliau or Kauai greensword [4] (Wilkesia gymnoxiphium) is related to the famous silverswords and greenswords found at high elevations on Maui and Hawaiʻi Island, both belong to the very large Asteraceae or Sunflower family of some 20,000 species worldwide! The genus Wilkesia is an endemic Hawaiian genus with only two incredible species.

Etymology

The generic epithet Wilkesia is named in honor of Captain Charles Wilkes (1798-1877), a commander of the United States Exploring Expedition.

The specific epithet gymnoxiphium is derived from the Greek gymno, naked or exposed, and xiphos, sword, in reference to the elongated sword-shaped leaves of this remarkable plant.

Background Information

Some who have read the book or seen the recent animation movie, like to call this plant the Lorax tree, after Dr. Seuss' "The Lorax."

This impressive species does well in lowland gardens growing to over 16 feet tall topped with a rossette of leaves. Unlike some Asteraceae relatives that are annual or perennial bloomers, iliau blooms once after several years of growth, flowers, sets its seed, and then dies. [4]

Though iliau closely related to naʻenaʻe (Dubautia spp.) no natural intergenetic hybrids have been found, unlike the silversword with more than thirty crosses between Dubautia and Argyroxiphium. [4]

There's an old saying that goes: ʻO ka iliau loho i ka lā, pūʻolo hau kakahiaka; The iliau plant drooping by day, the carrier of morning dew. [5]

Dwarf iliau

An extremely rare relative, also endemic to Kauaʻi, known as the Dwarf iliau (Wilkesia hobdyi), is scientifically named after its discoverer and botanist Robert Hobdy, a resident of Maui. This small plant is restricted to a few very dry ridges in its native habitat and usually blooms usually later from September to October, or even in December. [1] The dwarf iliau is an overall smaller plant around two feet tall, but still with an impressive floral display. [4] This species is found from 900 to around 1300 feet in elevation.

Early Hawaiian Use

Otto Degener in "Flora Hawaiiensis" [3] says that "Kauai Wilkesia ...is said to have been used medicinally by the ancient Hawaiians." Kaluna M. Kaʻaiakamanu confirms that iliau was used as medicine, but does not explain its application. [2]

Modern Use

Iliau can be seen in some botanical gardens. It does well in home landscapes with good sunlight and minimal water.

Additional References

[1] "The Status of the Genus Wilkesia" by Harold St. John, pages 129, 136.

[2] "Native Hawaiian Medicine--Volume III" by The Rev. Kaluna M. Kaʻaiakamanu, page 51.

[3] "Flora Hawaiiensis," by Otto Degener, Vols. 1-4, Family: 344.

[4] "Hawaiian Natural History, and Evolution" by Alan C. Ziegler, page 199.

[5] Hawaiian Dictionaries http://www.wehewehe.org [09/16/11]

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