Argyroxiphium sandwicense subsp. macrocephalum, the east Maui silversword

Lifecycle

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At senescence, which often occurs when the plant reaches a diameter of approximately , the plant produces a tall stalk in just a few weeks of maroon ray flowers which resemble the sunflower. Flowering usually occurs from July through October. The leaves become limp and dry as the monocarpic plant then goes to seed and dies.

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 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 National Park Service was granted control of Haleakalā volcano, visitors to the volcano's summit often participated in the common practice of uprooting a silversword plant and then rolling it on the jagged lava rock terrain, drying the flowers for arrangements, or using the plant as kindling. Because the delicate, shallow root structure can be crushed by walking in the rocks around the plant, they are very sensitive to foreign elements. Feeding by goats also severely damaged many plants and prevented reproduction. Ungulates are now fenced out of the crater area and the species is legally protected from damage by humans.

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File:Haleakala Silversword.jpg|Flower head bud, Haleakalā National Park

File:Silverswords on haleakala.JPG|Silverswords in bloom in Haleakalā crater

File:Argyroxiphium sandwicense macroencephalum.jpg|Haleakalā silversword at summit of Haleakalā National Park, Maui

File:Dying Haleakala silversword.JPG|Dying Haleakalā silversword after blooming at Haleakalā National Park, Maui

File:Argyroxiphium_sandwicense_Haleakala.jpg|Multiple rosettes indicate this individual may have Dubautia genes, although it does not have the yellow flowers of most hybrids.

File:Ahinahina flowers.jpg|Close-up of flowers

File:Haleakala-Silversword-Hawaii.jpg|Strong silver hairs cover the sword-like leaves.

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See also

  • Silversword alliance

References

  • Ka'ahele Hawaiʻi Native Plants
  • Federal recovery plan
  • Hawaiian Silversword Alliance, UH Botany
  • USDA Plants Profile for Argyroxiphium sandwicense subsp. macrocephalum (Hawaiʻi silversword)
  • USGS: Haleakalā Silversword (Argyroxiphium sandwicense subsp. macrocephalum)