Argyroxiphium sandwicense subsp. macrocephalum (A.Gray) Meyrat
Haleakala Silversword, East Maui Silversword
Argyroxiphium macrocephalum (basionym), Argyroxiphium sandwicense var. macrocephalum
Argyroxiphium sandwicense subsp. macrocephalum is a clumping perennial that forms rosettes of numerous fleshy, sword-like leaves covered with silver hairs. The rosettes grow up to 20 inches (50 cm) in diameter. A stunning, up to 6.6 feet (2 m) tall flower spike, with up to 600 heads of maroon ray flowers, appears after 15 to 50 years, and then the plant dies.
USDA hardiness zone 10a to 10b: from 30 °F (−1.1 °C) to 40 °F (+4.4 °C).
How to Grow and Care
The Silversword alliance comprises about 50 species of plants 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 after the seeds have been shed, the whole plant dies. 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 more delicate center of the plant from predation.
These attractive plants were previously collected as curiosities. Climbers on the mountains would dig them up as proof that 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 from the small size and range of their population, which is vulnerable to any chance event.
The Hawai'i Silversword is protected in Hawaii.
It is endemic to Hawaii (the island of Maui).
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