Argyroxiphium sandwicense subsp. macrocephalum
Haleakala silversword | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Clade: | Asterids |
Order: | Asterales |
Family: | Asteraceae |
Genus: | Argyroxiphium |
Species: | |
Subspecies: | A. s. subsp. macrocephalum
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Trinomial name | |
Argyroxiphium sandwicense subsp. macrocephalum (A. Gray) Mérat
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Argyroxiphium sandwicense subsp. macrocephalum, the east Maui silversword[1] or Haleakala silversword,[1] is a rare plant, part of the family Asteraceae. The silversword in general is referred to as ʻāhinahina in Hawaiian (literally, "very gray").
Distribution
The Haleakala silversword is found on the island of Maui at elevations above 2,100 metres (6,900 ft) on the dormant Haleakalā volcano—on the summit depression, the rim summits, and surrounding slopes—in Haleakalā National Park. The Haleakala silversword has been a
Description
The Haleakala silversword, Argyroxiphium sandwicense subsp. macrocephalum, has numerous sword-like
The plant's base of leaves, arranged in a spherical formation at ground level of the plant, dominates for the majority of the plant's life—which may be greater than 50 years. The leaves are arranged so that they and the hairs of the leaves can raise the temperature of the shoot-tip leaves up to 20 °C (68 °F), having adapted to the extreme high-altitude temperatures by focusing the sunlight to converge at this point and warm the plant.
The other subspecies, Argyroxiphium sandwicense subsp. sandwicense (Mauna Kea silversword), is found on Mauna Kea. They differ primarily in the inflorescence shape—broader in the Haleakalā plants (less than 4 times as long as wide) and narrower on Mauna Kea (4.3–8.6 times as long as wide). The Haleakala subspecies also generally has more ray florets, 11–42 versus 5–20 for Mauna Kea.[2]
Lifecycle
At
The flowering stalk may have up to 600 heads of up to 40 outlying ray flowers and 600 disk flowers and is pollinated by flying insects like Hylaeus (Nesoprosopis) volcanicus. The flower stalk can reach up to 2 metres (6.6 ft) in height and has numerous tiny sticky hairs to prevent crawling insects from damaging the plant. Seeding is a critical time because damage to the flowers or stalk by insects before the seeds can mature can jeopardize the plant's entire reproductive output.
History and conservation
Before the
Gallery
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Flower head bud, Haleakalā National Park
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Silverswords in bloom in Haleakalā crater
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Haleakalā silversword at summit of Haleakalā National Park, Maui
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Dying Haleakalā silversword after blooming at Haleakalā National Park, Maui
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Multiple rosettes indicate this individual may have Dubautia genes, although it does not have the yellow flowers of most hybrids.
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Close-up of flowers
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Strong silver hairs cover the sword-like leaves.
See also
References
- ^ . Retrieved 13 November 2021.
- ^ Wagner, W. L., D. R. Herbst, and S. H. Sohmer (1990). Manual of the Flowering Plants of Hawaii. Honolulu: University of Hawaii Press.
- ^ Plants of Hawaii: Argyroxiphium sandwicense subsp. macrocephalum
This article includes a list of general references, but it lacks sufficient corresponding inline citations. (July 2009) |
Reference links
External links
—Argyroxiphium sandwicense subsp. macrocephalum.