Hawaiian silversword (Argyroxiphium sandwicense)

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Hawaiian silversword in full flower
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Hawaiian silversword fact file

Hawaiian silversword description

KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderAsterales
FamilyCompositae
GenusArgyroxiphium (1)

The striking Hawaiian silversword stands out starkly against the volcanic landscape of its habitat. This plant consists of a rosette of narrow, pointed silver leaves that may be up to 40 centimetres long (2), together forming a silvery sphere (3). The common name for this species comes from the shape of the leaves; these are stiff, narrowly sword-shaped, and covered with silky, silver hair (2). These plants are particularly dramatic when in flower; the tall inflorescence grows up from the rosette of leaves and may reach three metres tall, and 75 centimetres wide (2). Between 50 and 600 compound flower heads are carried on the inflorescence; the individual flowers are pink or wine red in colour (2). Two subspecies are recognised; Argyroxiphium sandwicense subsp. macrocephalum has a more elliptical-looking inflorescence than A. s. subsp. sandwicense, which is thicker (2).

Also known as
East Maui silversword, Haleakala silversword, Mauna Kea silversword, silversword.
Size
Leaf length: 15 - 40 cm (2)
Inflorescence height: up to 3 m (2)
Leaf width: 0.5 - 1.5 cm (2)
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Hawaiian silversword biology

These plants only flower once in their lifetime, the silver rosettes grow for a number of years before the inflorescence ascends skywards (3). Flowers appear from mid-June to November (2), and after the seeds have been shed the whole plant dies (4). These exotic-looking plants are ideally suited to their harsh environment; the silver leaves reflect the sun's rays whilst their shape prevents moisture loss and protects the more delicate centre of the plant from predation (4).

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Hawaiian silversword range

Endemic to Hawaii, Argyroxiphium sandwicense macrocephalum is found on the island of Maui upon the Haleakala volcano, whilst A. s. sandwicense is found on Mauna Kea on the island of Hawaii itself (2).

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Hawaiian silversword habitat

Inhabits alpine cinder deserts, on Hawaiian volcanoes at heights of between 2,125 and 3,750 metres above sea level (2).

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Hawaiian silversword status

Classified as Vulnerable (VU) on the IUCN Red List (1). Subspecies: Argyroxiphium sandwicense sandwicense classified as Critically Endangered (CR), and A. s. macrocephalum classified as Vulnerable (VU) (1).

IUCN Red List species status – Vulnerable

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Hawaiian silversword threats

These attractive plants were previously collected as curiosities; climbers on the mountains would dig them up as proof that they had reached the summit (5). Populations were further depleted by browsing and trampling by goats and cattle in the area (3). Today A. s. sandwicense is restricted to a single population of as few as 30 plants in the Wailuku River basin on Mauna Kea in Hawaii (2). These plants are at risk from the small size and range of their population, which is vulnerable to any chance event that might occur.

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Hawaiian silversword conservation

The Hawaiian silversword is protected in Hawaii; A. s. sandwicense is listed as Endangered by the U.S. Fish and Wildlife Service whilst A. s. macrocephalum is listed as Threatened (6). On the island of Maui, the silversword is found within the Haleakala National Park, which was designated as an International Biosphere Reserve in 1980 (7). The U.S. Fish and Wildlife Service has produced Action Plans for the conservation of each subspecies (6), and the Haleakeala silversword has shown encouraging signs of recovery since it was first protected in the 1930s (5). This species is one of the many rare plants and animals found within the lunar landscape of the Haleakeala crater and can act as an important flagship species for conservation in the area (6).

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Find out more

For more information on the Hawaiian silversword see:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact: arkive@wildscreen.org.uk
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Glossary

Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Inflorescence
The reproductive shoot of the plant, which bears flowers.
Subspecies
A different race of a species, which is geographically separated from other populations of that species.
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References

  1. IUCN Red List (May, 2009)
    http://www.iucnredlist.org
  2. Wagner, W.L., Herbst, D.R. and Sohmer, S.H. (1999) Manual of the Flowering Plants of Hawaii, Vol. 1. University of Hawaii Press, Honolulu.
  3. Keck, D. (1936) The Silverswords of Hawaii. Carnegie Institution of Washington, News Service Bulletin, 4(8): 75 - 78.
  4. Islands – A Splendid Isolation(NHNZ tx. 1991).
  5. IUCN. (2001) The Red Book: The Extinction Crisis Face to Face. IUCN, Gland, Switzerland and Cambridge, UK.
  6. U.S. Fish and Wildlife Service (March, 2003)
    http://www.fws.gov/endangered
  7. Get Outdoors (May, 2009)
    http://www.getoutdoors.com/getoutdoors/destination_description/26.html
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Image credit

Hawaiian silversword in full flower  
Hawaiian silversword in full flower

© John Mason / www.ardea.com

Ardea wildlife pets environment
59 Tranquil Vale
London
SE3 0BS
United Kingdom
Tel: +44 (0) 208 318 1401
ardea@ardea.co.uk
http://www.ardea.com

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