Scientific Name
Argyroxiphium sandwicense subsp. macrocephalum (A.Gray) Meyrat
Synonym(s)
Argyroxiphium macrocephalum
Common Name(s)
Haleakala Silversword, East Maui Silversword
Scientific Classification
Family: Asteraceae
Subfamily: Asteroideae
Tribe: Madieae
Genus: Argyroxiphium
Etymology
The subspecific epithet "macrocephalum" (pronounced "mak-roh-SEF-uh-lum") means "large-headed". It refers to the more robust inflorescence of this subspecies, which is more elliptical-looking than that of Argyroxiphium sandwicense subsp. sandwicense, which is thicker.
Origin
Argyroxiphium sandwicense subsp. macrocephalum is endemic to Hawaii. It occurs at elevations between 7,000 and 10,000 feet (2,130 and 3,050 m) in the Haleakala National Park on the island of Maui.
Description
Argyroxiphium sandwicense subsp. macrocephalum is a beautiful, single-stemmed plant that forms distinctive, spherical rosettes of numerous sword-like, rigid, and succulent leaves covered with silver hairs. The leaves are usually three-angled in cross-section, measuring up to 16 inches (10 cm) long and 0.6 inches (1.5 cm) wide.
A stunning flower spike, which can grow up to 10 feet (3 m) tall, with up to 600 heads of densely packed pale red to maroon flowers, appears after 15 to 50 years. Each flower head has 11 to 42 petal-like ray florets and 50 to 600 tiny disk florets. The fruits are achenes that can grow up to 0.6 inches (1.5 cm) long. The plant is monocarpic, which means the rosette dies after the seeds ripen.
How to Grow and Care for Argyroxiphium sandwicense subsp. macrocephalum
Hardiness: USDA hardiness zone 10a to 10b: from 30°F (-1.1°C) to 40°F (4.4°C).
The Silversword alliance comprises about 50 plant species belonging to three genera endemic to the Hawaiian Islands. They get their common name from the visually impressive Silversword.
These plants only flower once in their lifetime. The silver rosettes grow for several years before the inflorescence ascends skywards. Flowers appear from mid-June to November, and the whole plant dies after the seeds have been shed. These exotic-looking plants are ideally suited to their harsh environment. The silver leaves reflect the sun's rays, while their shape prevents moisture loss and protects the plant's more delicate center from predation.
These attractive plants were previously collected as curiosities. Climbers on the mountains would dig them up to prove they had reached the summit. Populations were further depleted by browsing and trampling by goats and cattle in the area. Today, Argyroxiphium sandwicense is restricted to a single population of as few as 30 plants in the Wailuku River basin on Mauna Kea in Hawaii. These plants are at risk due to their small size and the limited range of their population, which is vulnerable to chance events.
The Hawai'i Silversword is protected in Hawaii.
Links
- Back to genus Argyroxiphium
- Succupedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus
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