Haleakala Silversword
Encyclopedia
The Haleakalā silversword (Argyroxiphium sandwicense subsp. macrocephalum) is a rare plant, part of the family
Asteraceae
. The silversword in general is referred to as āhinahina in Hawaiian
(literally, "very gray"). The Haleakalā silversword is found on the island of Maui
at an elevation of 2100 to 3000 m (6,889.8 to 9,842.5 ft) on the Haleakalā summit depression, the rim summits, and surrounding slopes of the dormant Haleakalā
volcano
, in and around Haleakalā National Park
.
The Haleakalā silversword has been a threatened species
as defined by the U.S. Fish and Wildlife Service, since May 15, 1992. Prior to that time, excessive grazing by cattle and goats, and vandalism inflicted by people in the 1920s, had caused its near extinction
. Since strict monitoring and governmental protection took effect, the species' recovery is considered a successful conservation story, although threats remain.
that is subject to freezing temperatures and high winds. The skin and hairs are strong enough to resist the wind and freezing temperature of this altitude and protect the plant from dehydration and the sun.
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 lifewhich 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), thereby having adapted to the extreme high-altitude temperatures by focusing the sunlight to converge at this point and warm the plant.
The other subspecies, A. sandwicense subsp. sandwicense
, is found on Mauna Kea
. They differ primarily in the inflorescence shapebroader 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 Haleakalā subspecies also generally has more ray florets, 11-42 versus 5-20 for Mauna Kea.
, which often occurs when the plant reaches a diameter of approximately one-half meter, the plant produces a tall stalk of maroon ray flowers which resemble the sunflower
in just a few weeks. Flowering usually occurs from July through October. This 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 two meters in height and has numerous tiny sticky hairs to prevent crawling insects from damaging the plant. Seeding of the plant is very sensitive because damage to the flowers or stalk by insects before reseeding further hinders the threatened species’ propagation. The leaves become limp and dry as the monocarpic
plant then goes to seed and dies.
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.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
. The silversword in general is referred to as āhinahina in Hawaiian
Hawaiian language
The Hawaiian language is a Polynesian language that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language of the state of Hawaii...
(literally, "very gray"). The Haleakalā silversword is found on the island of Maui
Maui
The island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
at an elevation of 2100 to 3000 m (6,889.8 to 9,842.5 ft) on the Haleakalā summit depression, the rim summits, and surrounding slopes of the dormant Haleakalā
Haleakala
Haleakalā , or the East Maui Volcano, is a massive shield volcano that forms more than 75% of the Hawaiian Island of Maui. The western 25% of the island is formed by the West Maui Mountains.- History :...
volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
, in and around Haleakalā National Park
Haleakala National Park
Haleakalā National Park is a United States national park located on the island of Maui in the state of Hawaii. The park covers an area of , of which is a wilderness area...
.
The Haleakalā silversword has been a threatened species
Threatened species
Threatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...
as defined by the U.S. Fish and Wildlife Service, since May 15, 1992. Prior to that time, excessive grazing by cattle and goats, and vandalism inflicted by people in the 1920s, had caused its near extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
. Since strict monitoring and governmental protection took effect, the species' recovery is considered a successful conservation story, although threats remain.
Physical characteristics
The Haleakalā silversword has numerous sword-like succulent leaves covered with silver hairs. Silversword plants in general grow on volcanic cinder, a dry, rocky substrateSubstrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
that is subject to freezing temperatures and high winds. The skin and hairs are strong enough to resist the wind and freezing temperature of this altitude and protect the plant from dehydration and the sun.
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 lifewhich 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), thereby having adapted to the extreme high-altitude temperatures by focusing the sunlight to converge at this point and warm the plant.
The other subspecies, A. sandwicense subsp. sandwicense
Mauna Kea silversword
The Mauna Kea silversword is a highly endangered flowering plant endemic to the Big Island of Hawaii. It is the "crown jewel" of the volcanic mountain, Mauna Kea, from which it derives its common name, and where it was once common. Extraordinary plant conservation efforts are being made to...
, is found on Mauna Kea
Mauna Kea
Mauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
. They differ primarily in the inflorescence shapebroader 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 Haleakalā subspecies also generally has more ray florets, 11-42 versus 5-20 for Mauna Kea.
Lifecycle
At senescenceSenescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
, which often occurs when the plant reaches a diameter of approximately one-half meter, the plant produces a tall stalk of maroon ray flowers which resemble the sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...
in just a few weeks. Flowering usually occurs from July through October. This 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
Hylaeus
Hylaeus can refer to:*Hylaeus and Rhaecus*Hylaeus, a genus of bees...
(Nesoprosopis) volcanicus. The flower stalk can reach up to two meters in height and has numerous tiny sticky hairs to prevent crawling insects from damaging the plant. Seeding of the plant is very sensitive because damage to the flowers or stalk by insects before reseeding further hinders the threatened species’ propagation. The leaves become limp and dry as the monocarpic
Monocarpic
Monocarpic plants are those that flower, set seeds and then die. Other terms with the same meaning are hapaxanth and semelparous. The term was first used by Alphonse de Candolle....
plant then goes to seed and dies.
History and conservation
Before the National Park ServiceNational Park Service
The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...
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.